Aleixo Technologies Software Engineer Interview Guide

The 60-second brief

Reports describe the Software Engineer role at Aleixo Technologies as infrastructure engineering with two named tracks: Cloud Network Engineer and Windows Engineer. The cloud track is described as work on network traffic in cloud environments, and the Windows track as managing Windows-based enterprise systems. Day to day, candidates report scoping, architecture reviews, implementation and post-deployment monitoring, plus automating manual processes and working with product managers and other engineering teams on new service deployments or upgrades.

This guide is for candidates interviewing for the Software Engineer role at Aleixo Technologies on either the cloud networking track or the Windows engineering track. It covers the three reported rounds, the reported questions (troubleshooting, protocols, availability, security, Windows operations and two experience-based prompts), the reported evaluation areas (VPCs, network security, PowerShell, Group Policy, performance monitoring) and a seven-day plan.

Candidates report 3 rounds over about 3-5 weeks: a Recruiter Screen, Technical Interviews that cover past projects and real-time problem solving, and Final Team Interviews. The number of sessions is reported to vary with the team and your seniority.

Focus areas

• Cloud Networking
• Network Engineering
• Windows Engineering

Overview

The Software Engineer title here maps onto infrastructure work rather than application development. The role is described as two tracks, Cloud Network Engineer and Windows Engineer, and the reported questions follow that split. On the cloud side they cover latency between cloud-hosted services, TCP versus UDP, high availability for virtual network appliances, exposing internal services to the public internet, and load balancing across regions. On the Windows side they cover deployment automation, kernel-level performance bottlenecks, patch compliance across a server fleet, Active Directory and hardening.

The requirements candidates describe ask for proficiency in either cloud networking (AWS, Azure or GCP) or Windows Server administration, scripting in PowerShell, Python or Bash, and experience with infrastructure-as-code and version control. Docker or Kubernetes, security compliance frameworks and 24/7 high-availability production experience are listed as extras. Pick your track early, but keep the shared ground sharp: a systematic troubleshooting method, a scripting habit and a security vocabulary are useful on both tracks.

Reports do not mention a dedicated algorithm round or a take-home. The technical stage is described as past projects plus real-time problem solving, so the most useful preparation is to rehearse spoken answers that move in a fixed order: scope the problem, name the layers or components, say how you would measure, state the trade-off, then say how you would verify the fix. For the cloud track, anchor on VPC subnets, routing tables and peering, firewall rules, security groups and encryption in transit. For the Windows track, anchor on PowerShell automation, Group Policy, performance counters and event logs.

Two reported prompts ask for personal experience: load balancing in a multi-region cloud environment, and resolving a complex Active Directory configuration issue. Candidates are also pointed to the STAR method, to quantifying outcomes such as uptime or latency, and to saying how you would find an answer when you do not know it. Build two or three project stories with your own role and measured results, because the project deep dives and the team interviews draw on them.

The Aleixo Technologies interview process

The three rounds below are what candidates describe, in the order they report them. The exact number of sessions can vary with the team and your seniority.

Recruiter Screen

The Recruiter Screen is reported as the first stage, an initial conversation about your fit and the role. Treat it as the place to settle which track you are interviewing for (cloud networking or Windows engineering) and to learn how the rest of the loop is organised for that team. Remote or hybrid arrangements are reported to depend on the team and location, so this is also where to ask about the work model.

What to demonstrate

• Fit for the role as a conversation about your background and what you want to do
• Which track your experience supports, cloud networking or Windows engineering
• Whether you can summarise your projects clearly and with outcomes

How to prepare

• Write a short summary of your career that names your track, your strongest platform (AWS, Azure, GCP or Windows Server) and one result you can quantify, such as uptime or latency.
• List the scripting languages you use (PowerShell, Python or Bash) and the infrastructure-as-code and version control tools you have worked with, since these appear in the reported requirements.
• Prepare questions about the stages that follow, the number of sessions for your team, and the work model (remote or hybrid) for the specific role.

Technical Interviews

The Technical Interviews are reported as in-depth sessions with engineering team members, focused on your past projects and real-time problem solving. Expect to explain how and why you built something, and to reason aloud through a fresh scenario. The reported technical questions are infrastructure scenarios, so practise answering them as a sequence: scope, components or layers, measurement, trade-off, verification.

What to demonstrate

• Depth in your own track, including the how and why of past implementations
• Problem solving worked out loud on a new scenario
• Troubleshooting method across network or Windows layers
• Awareness of trade-offs such as availability versus cost or exposure versus convenience

How to prepare

• Choose two past projects and be ready to defend the design, the alternatives you rejected and what you would change now.
• Rehearse the troubleshooting question about latency between two cloud-hosted services as a layered walk: DNS resolution, TCP connect, TLS handshake, server response time, then the network path.
• Rehearse the Windows kernel-level performance question using performance counters and event logs, ending with how you confirm the bottleneck rather than guess it.
• Practise the infrastructure-as-code and scripting parts of your answers so you can describe a real script or pipeline you wrote, including how it is versioned and tested.

Final Team Interviews

The Final Team Interviews are reported as the last stage, with the team, to evaluate cultural alignment and technical expertise. Reports also advise shifting from broad domain knowledge toward project-specific deep dives as you approach the final rounds. This is where the experience-based prompts (multi-region load balancing, an Active Directory issue) and collaboration stories are best rehearsed.

What to demonstrate

• Technical expertise in your track, with the reasoning behind decisions
• Communication and collaboration: explaining complex concepts and working with other teams
• Cultural alignment as the team sees it in how you describe past work

How to prepare

• Write STAR outlines for the multi-region load balancing story and the Active Directory story, each with your own decisions, the measured result and what you would change.
• Prepare an example of teaching a peer or learning from one, since collaboration with other teams is a reported part of the role.
• Prepare questions about the team's technology stack, team culture and long-term engineering goals, which candidates are advised to ask near the end.

Where candidates lose points

Answering the latency question by naming a cause (usually DNS or the firewall) before isolating anything

Give a fixed order: define the symptom and when it started, compare the path in both directions, then measure DNS lookup, TCP connect, TLS handshake and time to first byte separately. Say which tool you would use for each stage and what result would rule that stage out. Finish by saying how you would confirm the fix.

Defining TCP and UDP from a textbook without tying them to high-traffic applications

Tie each property to a traffic pattern: TCP gives ordering, retransmission and congestion control but pays with handshakes and head-of-line blocking. UDP gives low overhead and tolerance for loss, but the application owns reliability. Give an example of each, and say what you would choose for streaming, DNS and bulk transfer.

Treating exposure of an internal service as "put a firewall in front of it"

Describe layers: expose the smallest surface possible, terminate TLS, authenticate callers, scope security group and firewall rules to required ports and sources, rate-limit, log and alert, and keep the service patched. Mention segmentation so a compromise of the exposed tier does not reach the rest of the VPC.

Listing Windows tools (PowerShell, Group Policy, patching tools) without a process

For each Windows question, say the workflow: what you inventory first, how a change is staged on a pilot group before the fleet, how you report compliance, and how you roll back. For performance bottlenecks, name the counters and event logs you read and how you separate CPU, memory, disk and driver causes.

Telling project and Active Directory stories as "we" with no personal decision and no measured result

For every story, write one sentence on what you alone decided or built, and one number or observable result such as uptime or latency. Practise saying "I" for your actions and "the team" only for shared outcomes, and be honest where your experience stops.

Questions & practice

Identify the heaviest tenants in a five-minute window under memory pressure

Medium · top-k · heavy hitters · streaming

The edge service handles about 3,000 requests per second across roughly 50,000 tenants, peaking near 9,000. Expose the 50 heaviest tenants by request count over the trailing five minutes so limits can be tightened before one tenant's backfill starves the fleet. You may not retain five minutes of raw records. Give the exact solution and its memory, then the bounded-memory approximation with its error stated as a formula, and say which you would ship and at what tenant cardinality that choice changes.

Approach

1. Do the exact version first, because it is affordable at this cardinality: a ring of 300 one-second counters per tenant, advanced lazily, is 1,200 bytes of counters per tenant and roughly 60 to 90 MB for 50,000 tenants with overhead. Carry a running total and subtract the bucket you overwrite so a window read is O(1) rather than 300 adds.
2. Extract the top 50 with a size-k min-heap over the tenant sums: O(d log k) for d tenants, against O(d log d) to sort them all. Maintaining the heap continuously instead of on query requires a tenant-to-heap-index map, because incrementing a count already inside the heap means sifting from a known position, and without that map you rebuild the heap on every request.
3. State the approximation precisely rather than gesturing at sketches. Misra-Gries with m counters retains every item whose true count exceeds N/(m+1), and each retained count underestimates the truth by at most N/(m+1). With m = 1,000 and N = 900,000 requests in the window the error is roughly 900 requests, which is fine for spotting a tenant sending 50,000 and useless for ranking two tenants 200 apart.
4. Say what breaks when the window slides: Misra-Gries and Space-Saving are insert-only and cannot be decremented as records age out. The workable construction is one summary per sub-window, say ten seconds, with 30 summaries merged at query time, and the merged error is the sum of the per-summary errors, so the bound degrades linearly in the number of sub-windows.

Follow-up

• The heaviest tenant is heavy because of one export job rather than user traffic. Should the limiter treat those as the same tenant?
• Two tenants sit tied at the boundary of the top 50. Does your answer flap, and does the flapping matter?

Collapse a redelivered event batch into per-aggregate high-water marks

Easy · hashing · at-least-once · aggregation

You drain a batch of up to 5,000,000 events, each (aggregate_id BIGINT, aggregate_version INT, event_type, payload). The log guarantees order within one aggregate only; the batch merges 64 partitions, and a relay failover has redelivered a range, so an older version for an aggregate can appear after a newer one. Given a map of last_applied_version per aggregate, produce the events worth applying, at most one per (aggregate_id, version), plus the count discarded. Target O(n) time. State the memory for 2,000,000 distinct aggregates and what you do when it does not fit.

Approach

1. One pass, one hash map from aggregate_id to the highest version kept, and a discard counter. An event whose version is at or below last_applied_version for its aggregate is dropped without further work, which is the whole reason the event carries its version rather than a delta. O(n) expected time, O(d) space in distinct aggregates.
2. Keep the maximum, never the last occurrence. The redelivered range means the final appearance of an aggregate in the batch can be an older version than one seen earlier in the same batch, so last-wins applies stale state over newer state and the projection regresses with no error anywhere.
3. Cost the memory instead of calling it large: an 8-byte key plus a 4-byte version is 12 bytes of payload, and an open-addressed table held at a 0.7 load factor costs roughly 17 bytes per entry before per-slot metadata, so 2,000,000 aggregates is tens of megabytes in a native layout and several times that in a runtime that boxes both key and value.
4. If the distinct set exceeds memory, partition on hash(aggregate_id) mod P and reduce each partition independently. Every event for one aggregate hashes to the same partition, so the per-partition result is exact and the merge is concatenation rather than a second reduction.

Follow-up

• The payload is a patch rather than a snapshot, so applying only the highest version loses the intermediate changes. What changes in your reduction?
• How do you detect that version 7 arrived while version 6 was never delivered, and what should the consumer do about the gap?

Merge partitioned event streams into one ordered feed with bounded lateness

Hard · k-way merge · watermarks · out-of-order streams

The read-model service consumes 64 log partitions carrying about 4,000 events per second in total. Each partition is ordered within itself, but partitions drift by up to 30 seconds, and the activity feed must present a tenant's events in occurred_at order. Produce the merge. State its complexity, the buffer it requires in events and in bytes, what happens when one partition is idle, and what you do with an event that arrives after you have already emitted its position. Payloads average 1 KB.

Approach

1. Merge with a min-heap over the 64 partition heads keyed on (occurred_at, event_id): O(log P) per event and O(n log P) overall. The tie-break on event_id is what makes the output deterministic when two partitions carry the same millisecond, which matters because the feed is paginated and a non-deterministic order reorders pages under the reader.
2. Emitting the heap head is only correct once every partition has produced everything up to that timestamp, so the emit condition is a watermark: the minimum across partitions of the highest occurred_at seen, less the allowed lateness. Events are held until the watermark passes them, which is what turns individually ordered streams into a jointly ordered one.
3. Size the buffer from the lateness rather than guessing: 4,000 events per second times 30 seconds is 120,000 buffered events, and at 1 KB each about 120 MB of heap. That number is the real price of the ordering guarantee and belongs in front of whoever asked for it.
4. Handle the idle partition explicitly, because it fails the feed rather than corrupting it: a partition with no traffic never advances its own maximum, so the watermark freezes and output stops entirely. Either every partition emits a periodic idle marker carrying the broker's current time, or the watermark falls back to wall clock for a partition silent beyond a threshold.

Follow-up

• The lateness budget is raised to five minutes. What is the new buffer, and what besides memory changes?
• The consumer restarts. Where does it resume from, and what does the feed look like for the first 30 seconds?

Find version gaps and relay lag with window functions

Medium · window functions · event tables · frame semantics

outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.

Approach

1. Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
2. Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
3. Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
4. Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.

Follow-up

• Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
• Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?

Denormalise tenant onto revisions and backfill it live

Hard · denormalisation · online migration · backfill

resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.

Approach

1. Justify from the access path rather than from taste. Without the column, the audit feed either scans resource_revision by created_at and discards other tenants' rows, or resolves the tenant's resource_ids first and probes with them — both proportional to the tenant's whole history rather than to one page. With (tenant_id, created_at DESC, revision_id DESC) it is a seek that stops at 50 rows, and the purge becomes a ranged delete instead of a join.
2. Name the cost exactly: a second copy of a fact can disagree with the first. Make the disagreement unwritable rather than documented — add UNIQUE (resource_id, tenant_id) on resource so it can serve as a foreign-key target, then FOREIGN KEY (resource_id, tenant_id) REFERENCES resource (resource_id, tenant_id) on the revision table. A revision can then only ever carry its parent's tenant.
3. Step one, expand: ALTER TABLE resource_revision ADD COLUMN tenant_id BIGINT NULL, with no default, so it is a catalogue change and no rewrite. It still needs ACCESS EXCLUSIVE for an instant, and that instant queues behind the longest open transaction on the table while every later query queues behind it — set lock_timeout to 2s and retry rather than wait.
4. Step two, dual-write: deploy the writer that populates tenant_id on every new revision while reads still use the join. Reversible by redeploying the previous build, because nothing reads the column yet.

Follow-up

• The backfill is half finished and a rollback is required. What state is the table in, and what does the previous build do with a half-populated column?
• How do you verify the backfill actually finished, given rows are still being inserted while it runs?

These questions evaluate your fundamental understanding of network protocols, cloud architecture, and system a

Medium · Technical Infrastructure & Networking

These questions evaluate your fundamental understanding of network protocols, cloud architecture, and system administration.

Approach

1. Walk one request end to end and name the layer at each step: DNS resolution through a recursive resolver (and TTL caching), the TCP three-way handshake, the TLS handshake, then the HTTP request. For each step, say how it fails.
2. Explain cloud network layout: a VPC or VNet owns a CIDR block split into subnets. Route tables pick the next hop. A public subnet routes 0.0.0.0/0 to an internet gateway, while private subnets reach out through a NAT gateway.
3. Separate the two filtering layers. AWS security groups are stateful and attach to an instance or interface, so return traffic is allowed automatically. Network ACLs are stateless and apply per subnet, so return traffic needs explicit ephemeral-port rules.
4. Peering is not transitive: if A peers with B and B peers with C, A still cannot reach C through B. Larger topologies use a transit gateway or a hub-and-spoke design.
5. Name the host-level checks you actually run: ipconfig or ip addr, route print, netstat or ss for listening ports, nslookup or dig for DNS, and Test-NetConnection for a TCP port check on Windows.

Follow-up

• An instance in a private subnet cannot reach the internet. What do you check, and in what order?
• Why can two VPCs with overlapping CIDR ranges not be peered, and how would you connect them anyway?
• Return traffic is being dropped even though the inbound rule allows the request. Which layer do you suspect?

Explain the difference between TCP and UDP in the context of high-traffic network applications.

Medium · Technical Infrastructure & Networking

Approach

1. TCP is connection-oriented. It needs a three-way handshake, then delivers a reliable, ordered byte stream using retransmission, flow control (the receive window) and congestion control (slow start, then CUBIC or Reno-style backoff).
2. The price of TCP: a handshake round trip before any data, and head-of-line blocking, where one lost segment holds back all later data on that connection until it is retransmitted.
3. UDP is connectionless. It has an 8-byte header against TCP's 20-byte minimum and keeps message boundaries, but it gives no guarantee of delivery or order and has no congestion control. The application has to handle loss, ordering and pacing itself.
4. At high traffic, TCP keeps per-connection state on servers and load balancers. TIME_WAIT builds up on whichever side closes first, and ephemeral ports can run out, so connection pooling and keep-alive matter. UDP fits DNS, real-time media, game state and telemetry, where late data is worthless.
5. Name the risks and the modern middle ground. UDP sources can be spoofed, which enables reflection and amplification attacks, and datagrams larger than the path MTU fragment and get dropped. QUIC (HTTP/3) runs over UDP to avoid TCP head-of-line blocking across streams and to merge the transport and TLS handshakes.

Follow-up

• Why does DNS mostly use UDP, and when does it switch to TCP?
• How does a load balancer track UDP flows when there is no connection to track?
• What is TIME_WAIT, and why might it pile up on a busy server?

How do you ensure high availability when configuring virtual network appliances?

Medium · Technical Infrastructure & Networking

Approach

1. Remove single points of failure. Run at least two appliances in separate availability zones or fault domains, then choose between active-passive (state sync, with failover by moving a floating IP or rewriting a route table) and active-active behind a load balancer.
2. Use the platform's built-in pattern. Azure uses an internal Standard Load Balancer with an HA ports rule in front of network virtual appliances. AWS uses a Gateway Load Balancer, which wraps traffic in GENEVE to reach third-party appliances.
3. Keep routing symmetric. A stateful firewall has to see both directions of a flow. In active-active, flow hashing or SNAT must send return traffic to the same appliance, or the session is dropped.
4. Make the health probe test the data path, not just the management interface. An appliance can answer a probe while forwarding nothing. Balance fast detection against flapping, and sync session state so failover does not reset established connections.
5. Keep appliance configuration in version control and apply it the same way to every node. Upgrade one node at a time, and test failover by stopping a node and measuring how long convergence takes and how many sessions drop.

Follow-up

• Established connections drop after an active-active failover. Why, and how do you prevent it?
• The appliance passes its health probe but silently drops forwarded traffic. How would you detect that?
• How do you upgrade appliance firmware without an outage?

What are the security considerations when exposing internal services to the public internet?

Medium · Technical Infrastructure & Networking

Approach

1. First ask whether the service needs to be public at all. A VPN, private endpoint or PrivateLink-style connection may meet the need. If it must be public, keep the service in a private subnet behind a load balancer, reverse proxy or API gateway, allow only 443, and let the service accept traffic only from that front end.
2. Terminate TLS with valid certificates and TLS 1.2 or later, enable HSTS, and decide whether to re-encrypt between the proxy and the backend.
3. Add real authentication and authorization. An internal service often assumed the network was trusted. Put OIDC/OAuth2 or mTLS in front of it, check authorization per endpoint, and remove admin, debug and metrics endpoints from the public route.
4. Protect against abuse. Use WAF rules for common injection classes, rate limits, request size limits and input validation, plus the provider's DDoS protection.
5. Cover what happens after a compromise. Restrict egress, block SSRF paths to the metadata endpoint at 169.254.169.254 (AWS IMDSv2 requires a session token), keep secrets out of code, log access centrally and keep the exposed stack patched.

Follow-up

• The service identifies clients from the X-Forwarded-For header. What can go wrong?
• For a partner integration, would you pick a VPN, a private endpoint or a public endpoint with mTLS, and why?
• How would you stop the exposed service from being used to reach other internal systems?

These questions focus on your proficiency with the Windows ecosystem and your ability to manage enterprise-gra

Medium · Windows Systems & Operations

These questions focus on your proficiency with the Windows ecosystem and your ability to manage enterprise-grade server environments.

Approach

1. Cover Active Directory basics: domain controllers, FSMO roles, sites and replication. AD depends on DNS, because clients find domain controllers through SRV records, so a broken DNS setup often looks like an AD failure.
2. Explain Group Policy processing order: local, site, domain, then OU (LSDOU). The policy applied last wins a conflict unless a higher link is Enforced, and gpresult /r shows what actually applied.
3. For management, cover PowerShell remoting over WinRM and DSC or Ansible for configuration. Compare Server Core with Desktop Experience: Core has a smaller attack surface and fewer patches but harder local troubleshooting.
4. For operations, read the System, Application and Security event logs, use Performance Monitor counters for CPU, memory, disk and network, and keep a baseline so you can tell what is abnormal.
5. Base the answer on an environment you actually ran: which roles it hosted, what you automated and what broke. Be clear about which side you know more deeply, cloud networking or Windows.

Follow-up

• A client cannot log on to the domain. Which DNS records and services do you check first?
• Two GPOs set the same setting differently. How do you find out which one won?
• Why might you run a domain controller on Server Core?

What tools do you use for automating Windows server deployments?

Medium · Windows Systems & Operations

Approach

1. Answer in layers. Image build: MDT or WDS on premises, or Packer or Azure Image Builder in the cloud. Provisioning: Terraform, Bicep or ARM, or CloudFormation. Configuration: PowerShell DSC, Ansible over WinRM, or Group Policy. Lifecycle: Configuration Manager or Intune.
2. Generalize the image with Sysprep /generalize before capturing it. This strips machine-specific identity such as the SID so clones do not collide, and an unattend.xml answer file completes setup without anyone at the console.
3. Make every step idempotent. DSC resources test current state before setting it, and plain scripts should check before they change anything. Keep everything in version control and run it through a reviewed CI pipeline, not from someone's desktop.
4. Keep credentials out of scripts. Pull them from a vault at runtime, use group managed service accounts for services, and use offline domain join (djoin) or a vault-held join account for domain join.
5. Verify the result. Pester tests check the built server against the declared configuration, and drift reports or periodic DSC consistency checks catch manual changes later.

Follow-up

• How do you stop a deployed server from drifting away from its declared configuration?
• What breaks if you clone a Windows image without generalizing it?
• How does your pipeline join a server to the domain without a plaintext password?

Explain the process of diagnosing a kernel-level performance bottleneck on a Windows server.

Medium · Windows Systems & Operations

Approach

1. First confirm the time is spent in the kernel. In Performance Monitor, compare % Privileged Time with % User Time. High % Interrupt Time or % DPC Time points to a driver or hardware, usually the NIC or storage.
2. Check kernel memory. Steady growth in Pool Nonpaged Bytes or Pool Paged Bytes suggests a driver leak. poolmon sorts usage by pool tag, and matching the tag to a .sys file names the driver.
3. Check storage. Avg. Disk sec/Read and sec/Write show latency, and queue length shows backlog. fltmc lists file system filter drivers, such as antivirus, that add work to every I/O.
4. Capture a trace. Windows Performance Recorder records ETW with CPU sampling and DPC/ISR events, and Windows Performance Analyzer with symbols loaded shows which module and stack consume the time. Keep the capture short, because tracing adds overhead.
5. Fix and verify. Update or roll back the driver or firmware, check NIC settings such as RSS and interrupt moderation, then compare against the baseline. For a hang, take a kernel memory dump and analyse it in WinDbg.

Follow-up

• % DPC Time is high on one core only. What does that suggest about the network adapter?
• How would you find which driver is leaking nonpaged pool?
• How do you limit the impact of tracing on a production server?

How do you manage patch compliance across a large-scale server fleet?

Medium · Windows Systems & Operations

Approach

1. Name the tooling: WSUS, Configuration Manager or Azure Update Manager for servers, with approvals managed per deployment ring. Group servers by role and criticality so every server has a maintenance window and an owner.
2. Roll out in rings: a pilot group first, then wider waves, with health checks between them. Use Cluster-Aware Updating to drain and patch failover cluster nodes one at a time, and patch one side of every HA pair at a time.
3. Define compliance precisely: every approved security update installed within a deadline set by severity, with a pending reboot counted as non-compliant. Report per server from the tool's inventory, not from what was deployed.
4. Handle the exceptions. Retry failed installs, catch up servers that were offline during their window, and record each exemption with an owner, a reason and an expiry date. Keep a rollback path, such as snapshots or uninstalling the KB, plus post-patch smoke tests.
5. Keep a separate expedited path for an actively exploited CVE that skips the normal ring schedule but still starts with a small group.

Follow-up

• A patch breaks an application in the pilot ring. What happens to the rest of the rollout?
• How do you patch a two-node cluster without downtime?
• A server owner refuses every reboot window. How do you handle that server?

What strategies do you employ to secure Windows environments against common vulnerabilities?

Medium · Windows Systems & Operations

Approach

1. Start from a baseline: CIS Benchmarks or Microsoft security baselines applied through Group Policy. Disable SMBv1, require SMB signing, turn off LLMNR and NetBIOS name resolution where unused (both enable poisoning and relay attacks), and restrict NTLM where possible.
2. Harden identity. Use a tiered admin model with no domain admin logons on ordinary servers or workstations. Use LAPS so local admin passwords are unique, which blocks lateral movement with a shared hash. Add Credential Guard to protect LSASS secrets, the Protected Users group and MFA for privileged access.
3. Shrink the attack surface: patch promptly, remove unused roles and features, prefer Server Core, set host firewall rules, and enforce application control with WDAC or AppLocker plus Defender attack surface reduction rules.
4. Make attacks visible. Forward Security log events centrally (4624 and 4625 logons, 4688 process creation, 4720 account creation), add Sysmon or EDR, and audit AD for service accounts with SPNs and weak passwords, which are Kerberoasting targets.
5. Plan for recovery: offline or immutable backups and tested restores, so ransomware cannot also destroy the way back.

Follow-up

• How does LAPS limit lateral movement after one server is compromised?
• What is Kerberoasting, and how would you reduce exposure to it?
• How would you enforce SMB signing without breaking older devices?

How would you troubleshoot a latency issue between two cloud-hosted services?

Medium · Technical Infrastructure & Networking

Approach

1. Scope it before forming a theory. Is it every request or only the tail (p50 vs p99)? One direction, one zone or one region? Since when? Then line the start time up against deploys, scaling events and config changes.
2. Split the latency into phases. curl -w with time_namelookup, time_connect, time_appconnect and time_starttransfer separates DNS, TCP connect, TLS handshake and time to first byte, which tells you whether the network or the server is slow.
3. If connect time is high, look at the path. Check for cross-zone or cross-region hops, an extra proxy or NAT hop, packet loss and retransmissions (ss -ti shows rtt and retrans), and MTU black holes where path MTU discovery is blocked.
4. If connect time is normal but time to first byte is high, the server side is slow. Check CPU, garbage collection pauses, thread or connection pool exhaustion and slow downstream calls, and use tracing spans to find the slow hop.
5. Check client behaviour too. Missing keep-alive forces a new handshake on every request, SNAT port exhaustion shows up on NAT or load balancer metrics, and a stale DNS cache can send traffic to drained endpoints. Re-measure the same way after the fix.

Follow-up

• p50 is unchanged but p99 tripled after one service moved to another availability zone. What do you suspect first?
• How would you show that packet loss is the cause of the latency rather than a side effect of overload?
• Handshake times are normal but time to first byte is high. Where do you look next?

Suggested practice checklist

Seven days built around the two tracks this loop reports: three days on cloud networking and security, Windows operations and Active Directory, a scripting day, then a full mock. Each day ends with something you can show.

Day 1 — Pick your track and map the loop

• Write the three reported rounds (Recruiter Screen, Technical Interviews, Final Team Interviews) and, next to each, the two or three things you must be able to say in it.
• Decide whether you are presenting as a cloud networking or a Windows engineer, then list your three strongest projects on that track with one measured result each.
• Write the ten words you would use for the requirements candidates describe (PowerShell, Python, Bash, infrastructure-as-code, version control and so on) and mark which ones you can demo.

Deliverable: A one-page loop map plus a ranked list of three projects, each with a measured result, and a marked list of skill gaps.

Day 2 — Cloud networking: latency, protocols and appliance availability

• Sketch a VPC with public and private subnets, route tables and one peering link, and trace a request between two services across it.
• Write a latency troubleshooting sequence for "How would you troubleshoot a latency issue between two cloud-hosted services?": DNS, connect, TLS, first byte, path, with the tool and expected finding at each step.
• Answer aloud "Explain the difference between TCP and UDP in the context of high-traffic network applications." and "How do you ensure high availability when configuring virtual network appliances?", covering active-passive versus active-active, health probes and route failover.

Deliverable: A VPC diagram, a one-page latency checklist and a spoken answer to each of the two questions.

Day 3 — Security exposure and multi-region load balancing

• List the controls for exposing an internal service to the public internet: minimal ports, TLS, authentication, security group scope, rate limiting, logging, segmentation. Rank them by what you would do first.
• Draw a multi-region load balancing layout with global steering, regional balancers, health checks and the data layer, and mark what happens when one region fails.
• Write the STAR outline for "Describe your experience with load balancing strategies in a multi-region cloud environment." using a real project, with the result in numbers.

Deliverable: A ranked exposure checklist, a multi-region diagram with the failure path marked, and a one-page STAR outline.

Day 4 — Windows operations: automation, performance and patching

• Write a PowerShell script that reads a list of servers, collects patch or hotfix status and writes a CSV compliance report, then describe how you would schedule and stage it.
• Outline an answer to "What tools do you use for automating Windows server deployments?" in a pipeline order: build image, configure, validate, record state.
• Walk through "Explain the process of diagnosing a kernel-level performance bottleneck on a Windows server." with counters for CPU, memory, disk and network and the event logs you would read.
• Answer "How do you manage patch compliance across a large-scale server fleet?" including pilot groups, maintenance windows, reporting and rollback.

Deliverable: A working compliance-report script, a deployment pipeline outline and a counter-by-counter diagnosis sheet.

Day 5 — Active Directory and Windows hardening

• Write the STAR outline for "Describe a time you had to resolve a complex Active Directory configuration issue." with the diagnostic order (DNS, replication, time, sites, Group Policy results), the fix, the safety steps and the verification.
• List a hardening baseline for "What strategies do you employ to secure Windows environments against common vulnerabilities?": patching, least privilege, Group Policy security settings, logging, and how you audit them.
• Practise saying both stories aloud in your own voice, then cut every sentence that does not show a decision you made.

Deliverable: A one-page Active Directory story, a hardening checklist with an audit step for each item and a recorded spoken run-through.

Day 6 — Scripting fluency and live problem solving

• Write one small automation in Python or Bash (for example a health check across hosts that reports failures) and put it under version control with a clear commit history.
• Describe, in words, how you would express a network or server change as infrastructure-as-code and test it before applying it.

Deliverable: A committed automation script with a short README, a written infrastructure-as-code outline and two solved practice problems.

Day 7 — Full mock and questions for the team

• Run a spoken mock that mixes one project deep dive, one cloud troubleshooting scenario, one Windows scenario and one experience story, and record it.
• Review the recording for places where you guessed, rambled or used "we" without an "I", and fix those answers.
• Write the questions you will ask the team about the stack, team culture and long-term engineering goals, and one question for the recruiter about the work model.

Deliverable: A recorded mock with a list of fixes made, and a final list of questions for the team and the recruiter.

Experience stories for infrastructure roles

The reported experience prompts are about cloud load balancing and Active Directory troubleshooting, so the stories need real technical content: what you decided, what you measured and what you would change. Candidates are advised to use the STAR method, to highlight outcomes such as uptime or latency, and to say how they would find an answer when they do not know it. Collaboration with other teams is part of the role as reported, so prepare one story about explaining something technical to a non-specialist or learning from a peer.

1. Tell me about an automation you built to replace a manual operations task, and the result it produced.
2. Tell me about a time you did not know the answer to a technical question and how you found it.
3. Tell me about a time you explained a complex technical concept to another team and what changed as a result.

Describe your experience with load balancing strategies in a multi-region cloud environment.

Medium · Technical Infrastructure & Networking

Approach

1. Treat this as a STAR story with technical content, and do not recite a vendor feature list. Say which cloud, which regions, what traffic (HTTP APIs, long-lived connections, internal services) and what you personally owned: design, rollout, failover testing or the on-call burden.
2. Show that you understand the layers. Global steering usually happens first, through DNS-based routing (latency, geolocation or weighted records) or an anycast or global load balancer. Inside each region a layer 4 or layer 7 balancer spreads traffic across instances. Name the algorithm you used (round robin, least connections or weighted) and why it fitted the workload.
3. Cover health and failure. Describe the health checks (what they probe, how often, how many failures remove a target), how traffic moved when a region was impaired, and the effect of DNS TTLs and client caching on how fast it moved. Mention how you tested failover rather than assuming it works.
4. Address state. Session affinity, session stores, database replication lag and data residency decide whether active-active is safe or whether active-passive is the honest answer. Add the cost side, such as cross-region data transfer, and a measured result, for example error rate or latency during a regional failure.
5. If your experience is at a single region or on a different platform, say so, describe what you did build, and walk through how you would extend it across regions. Explaining how you would find the missing pieces is better than overstating.

Follow-up

• What happens to in-flight requests and user sessions when a region fails, and how long until traffic fully moves?
• How did you test the failover, and what did the test reveal that the design did not predict?
• Would you run this active-active or active-passive, and what does the database layer do to that choice?

Describe a time you had to resolve a complex Active Directory configuration issue.

Medium · Windows Systems & Operations

Approach

1. Pick an issue you resolved yourself, and open with the symptom and its scope in two sentences: logons failing, a policy not applying, replication errors between sites or a trust breaking. State who was affected and what the risk was.
2. Walk through the diagnostic order, because that is what shows depth. Typical steps are checking DNS and the SRV records that clients use to find domain controllers, checking replication health between controllers (replication summary and domain controller diagnostics tools), checking time sync because Kerberos is sensitive to clock skew, then checking sites and subnets, SYSVOL replication and Group Policy results on an affected client (gpresult, gpupdate).
3. Name the root cause and the change you made, then the safety around it: how you limited blast radius (one site or one test organisational unit first), what you backed up, and what you avoided doing, such as forcing role seizure or deleting objects before establishing the cause.
4. Close with verification and prevention: how you proved the fix (replication converged, policy applied on a fresh logon, errors cleared in event logs) and what you changed afterwards, such as monitoring on replication health, a documented runbook or a change review.
5. The common mistake is a story with no root cause ("I restarted the service and it went away") or one told entirely as "we". Make your own actions and your reasoning clear, and give one thing you would do differently.

Follow-up

• How did you confirm that replication or policy application had really converged everywhere, and not only on the machine you tested?
• What did you rule out first, and why was that the cheapest check?
• What did you put in place so the same configuration issue would be caught earlier next time?

Unblock an engineer without taking the keyboard

Easy · mentoring · leases · at-least-once

A teammate has spent two days on a job handler that occasionally writes duplicate rows. They are certain the queue is delivering twice by mistake. You suspect a lease expiring under a slow handler, so the job is running concurrently with itself. Describe how you have unblocked someone in this position: what you asked before offering a hypothesis, what you showed them rather than told them, and what you left them owning. Then say what you would do if their theory turned out to be the right one.

Approach

1. Ask before diagnosing, and ask for things answerable from data they already have: the attempt count on the job rows that produced duplicates, the handler's observed duration against its lease expiry, and whether the duplicate rows share a natural key that a unique constraint could have caught.
2. Teach the shape rather than the answer. A lease cannot distinguish a dead worker from a slow one, so a handler that outruns its lease is running twice by design, and deploys deliver the other half by killing handlers mid-run on every rollout. Both of their candidate theories produce identical duplicate rows, which is why the evidence has to come from timings rather than from argument.
3. Hand over a checklist they execute: a natural key on every write the handler performs so the second copy collides rather than appends, the record of intent written before any external effect, a lease heartbeat while running, and the metric that shows it working.
4. Keep ownership with them deliberately. Pair on the first write, then step back; if you finish it yourself you have closed one ticket and left the same person stuck on the next redelivery.

Follow-up

• How would you distinguish a genuine double-delivery from a lease expiry using only the data already stored?
• Their handler calls an external endpoint before recording that it did. What do you tell them to change first?