Interview guides · Halvik

Halvik Software Engineer Interview Guide

Halvik Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

At Halvik, a Software Engineer plays a pivotal role in designing, developing, and modernizing robust technology solutions that support critical enterprise and public sector missions. Working at Halvik means building highly secure, scalable, and resilient applications that directly impact government agencies, enterprise partners, and millions of end-users. Engineers here do not just write code; they solve complex architectural challenges, migrate legacy systems to modern cloud environments, and implement cutting-edge platforms to streamline workflows. The engineering organization at Halvik is structured around cross-functional, agile teams specializing in areas such as full-stack web application development, cloud systems engineering, and enterprise platform customization (including Salesforce).

This guide is scoped to a Software Engineer candidate at Halvik.

Focus areas

Web Application Development
Full-Stack Development
Backend Development

The Halvik interview process

Halvik candidates report 3 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Conversational Screening

Initial discussion with a recruiter to align on background, career goals, and compensation expectations.

What to demonstrate

Initial discussion with a recruiter to align on background, career goals, and compensation expectations
Depth in Web Application Development

How to prepare

Answer aloud and timed: Explain the difference between client-side rendering and server-side rendering, and when you would choose one over the other.
Answer aloud and timed: How do you secure a RESTful API against common vulnerabilities such as SQL injection and Cross-Site Scripting (XSS)?

Technical Evaluation

Assessment that may include a live coding session, technical discussion with a senior engineer, or platform-specific deep dive.

What to demonstrate

Assessment that may include a live coding session, technical discussion with a senior engineer, or platform-specific deep dive
Depth in Web Application Development

How to prepare

Answer aloud and timed: Describe how you would manage state across a large-scale React or Angular application.
Answer aloud and timed: What is the event loop in JavaScript, and how does it handle asynchronous operations?

Comprehensive Panel Interview

Final interview with engineering leaders and project stakeholders to discuss system design, behavioral scenarios, and team fit.

What to demonstrate

Final interview with engineering leaders and project stakeholders to discuss system design, behavioral scenarios, and team fit
Depth in Web Application Development

How to prepare

Answer aloud and timed: How do you optimize the loading performance of a heavy, data-driven web application?
Answer aloud and timed: Describe your experience setting up and maintaining CI/CD pipelines using tools like Jenkins, GitLab CI, or GitHub Actions.

Where candidates lose points

Focus on the "Why

When writing code or designing a system, always explain your reasoning out loud. Your interviewer is more interested in your thought process, how you handle edge cases, and how you evaluate trade-offs than they are in syntax memorization.

Be Agile-Ready

Be prepared to discuss how you collaborate in a fast-paced agile environment. Use examples that highlight your experience with continuous integration, automated testing, and active participation in sprint ceremonies.

Saying 'eventually consistent' without naming the anomaly a user would see

Describe the concrete symptom you are choosing to accept: the author reloads and their own comment is missing for two seconds, or two devices show different balances for a minute. The class of consistency model is a technical label; the tolerable anomaly is the actual product decision.

Questions & practice

What is the event loop in JavaScript, and how does it handle asynchronous operations?

Medium · Web Development & Full-Stack Architectur

Approach

Say what the runtime actually does before reasoning about the code.
Name what is shared across threads and what owns each piece of state.
Identify the window where an invariant is briefly untrue.
Distinguish a value from a reference to it, and say which one you handed out.

Follow-up

What happens if two callers reach this at the same time?
Where could this allocate more than you expect?

Archive a resource graph without breaking live references or recursing

Medium · graph traversal · topological order · tenant isolation

Resources reference other resources within a tenant; for the largest tenant the reference table holds up to 2,000,000 nodes and 8,000,000 edges. Archiving a resource must archive everything reachable from it that nothing outside the set still references, refuse when a live external referrer exists, and terminate when references form cycles, which they legitimately do. Produce the archive order and the refusal list, targeting O(V+E). Say what stops the traversal crossing a tenant boundary, and why recursion is the wrong control structure at this size.

Approach

Load the subgraph with the tenant predicate on both endpoints of the edge, not only on the side you started from. Scoping the left table alone is the classic cross-tenant leak: one mis-entered edge then pulls another tenant's resources into the traversal and, worse, into the archive.
Traverse iteratively with an explicit stack. A 2,000,000-node graph can hold a chain deep enough to exhaust a native stack in the low tens of thousands of frames, and that failure is a process crash rather than an error you can return.
Treat cycles as data rather than corruption: compute strongly connected components with Tarjan in O(V+E) using its own explicit stack, then condense. The condensation is a DAG, so a topological order over it gives the archive order, and every member of a component archives in one transaction because no order within a cycle is valid.
Decide refusals with reverse edges. A candidate is archivable only if every in-edge originates inside the candidate set, so build the transpose or count in-degrees restricted to the visited set, and emit each blocked resource with the id of the external referrer, which is the only part of the answer an operator can act on.

Follow-up

The graph is read in one query and the archive writes a minute later. What can change in between, and how do you make the write safe?
The candidate set is 400,000 resources. Is that one transaction, and if not, what does a half-finished archive look like to a reader?

Canonicalise a request body into a stable idempotency fingerprint

Medium · parsing · canonicalisation · hashing

idempotency_key.request_fingerprint is a SHA-256 over the method, path and canonicalised body, and a retry whose fingerprint differs must be rejected with 422 rather than served the stored response. Write the canonicaliser. Bodies are JSON up to 256 KB nested at most 32 levels; clients vary key order, whitespace and unicode escaping, and some send 64-bit ids as JSON numbers. Produce a deterministic byte string such that semantically identical bodies match and any semantic difference does not. State your complexity and name two normalisations you refuse to perform.

Approach

Parse once into a tree, then re-serialise under fixed rules: object keys sorted, array order preserved, one escaping convention, no insignificant whitespace. Parsing is O(n) and sorting keys is O(k log k) per object, so O(n log n) overall with O(depth) stack, and the 32-level cap is enforced during parsing because hostile nesting is how a canonicaliser becomes a stack overflow.
Sort keys by their UTF-8 bytes and say why the obvious implementation is wrong in some runtimes: a default string comparison that orders by UTF-16 code units places surrogate pairs, meaning code points from U+10000 up, below U+E000 to U+FFFF, which is not UTF-8 byte order, so two services written in different languages disagree on the same document.
Do not re-encode numbers through a double. IEEE-754 binary64 represents integers exactly only up to 2^53, so normalising a 19-digit id through a float changes it, and 1 against 1.0 cannot be reconciled without deciding whether they are the same value. Preserve the literal token, and require ids as strings at the API boundary if you want them comparable.
Reject duplicate keys rather than picking one. JSON permits them and parsers disagree, most keeping the last, so any choice you make ties the fingerprint to a parser detail that the code handling the request does not necessarily share.

Follow-up

A client sends the same logical request with an extra field your API ignores. Same key, different fingerprint, so you return 422. Is that the right answer?
Where does the fingerprint get computed relative to request decompression and the body-size limit?

Hold a per-tenant active cap against concurrent creates

Hard · write skew · isolation levels · constraints

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

Approach

Name it: write skew. The two transactions read an overlapping set and write disjoint rows, so there is no row-level conflict for the engine to detect and each commit is individually legal.
Rule out the levels precisely. READ COMMITTED takes a fresh snapshot per statement and takes no lock on the counted rows, so both see 49. PostgreSQL's REPEATABLE READ is snapshot isolation: it removes non-repeatable reads and phantoms within the snapshot but still admits write skew, because the anomaly is not a re-read of a changed row, it is a read of a set that a concurrent transaction invalidates. Only SERIALIZABLE closes it, by tracking the read dependency and aborting one transaction with SQLSTATE 40001 — a guarantee that exists only if the application re-runs the whole transaction from the read.
Convert the set predicate into a single-row conflict: keep tenant.active_resource_count and run UPDATE tenant SET active_resource_count = active_resource_count + 1 WHERE tenant_id = $1 AND active_resource_count < 50 in the same transaction as the INSERT. Zero affected rows is the cap, returned as 409. The row lock serialises the decision at any isolation level, and contention is bounded to one tenant's row — which is also the fair-scheduling unit, unlike a global counter that would convoy every tenant behind one row.
State the cost you just took on: a counter is a second source of truth that can drift, so every path that changes status must adjust it inside the same transaction, and a periodic reconciliation has to exist, with resource_revision as the authority for what the count should have been.

Follow-up

A resource moves from archived back to active. Which statements change, and what breaks if the counter update and the status change land in different transactions?
The cap becomes plan-dependent and a plan can change mid-month. Where does the number 50 live, and who reads it?

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

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.
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.
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.
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?

Explain the difference between client-side rendering and server-side rendering, and when you would choose one

Medium · Web Development & Full-Stack Architectur

Explain the difference between client-side rendering and server-side rendering, and when you would choose one over the other.

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How do you secure a RESTful API against common vulnerabilities such as SQL injection and Cross-Site Scripting

Medium · Web Development & Full-Stack Architectur

How do you secure a RESTful API against common vulnerabilities such as SQL injection and Cross-Site Scripting (XSS)?

Approach

Say who the caller is and what they do when the call fails halfway.
Define the identity of a request so a retry cannot double-apply it.
Separate accepted, pending, failed and confirmed; they are different facts.
Design the error taxonomy before the success shape; callers branch on it.

Follow-up

What happens if the caller retries after a timeout?
How does a client discover it is on an old version of this contract?

Describe how you would manage state across a large-scale React or Angular application.

Medium · Web Development & Full-Stack Architectur

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How do you optimize the loading performance of a heavy, data-driven web application?

Medium · Web Development & Full-Stack Architectur

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

What are the primary benefits of containerization with Docker, and how do you orchestrate containers using Kub

Medium · Systems Engineering & Cloud Infrastructu

What are the primary benefits of containerization with Docker, and how do you orchestrate containers using Kubernetes?

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How would you design a highly available, fault-tolerant architecture on AWS or Azure for a web application?

Medium · Systems Engineering & Cloud Infrastructu

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

Explain the concept of Infrastructure as Code (IaC) and how you have used tools like Terraform in past project

Medium · Systems Engineering & Cloud Infrastructu

Explain the concept of Infrastructure as Code (IaC) and how you have used tools like Terraform in past projects.

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How do you monitor system health and set up alerting for a distributed microservices architecture?

Medium · Systems Engineering & Cloud Infrastructu

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

Explain the difference between declarative customization (flows, validation rules) and programmatic customizat

Medium · Platform-Specific & Salesforce Developme

Explain the difference between declarative customization (flows, validation rules) and programmatic customization (Apex, Lightning Web Components) in Salesforce.

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Describe how you would integrate an external ERP system with Salesforce using REST or SOAP APIs.

Medium · Platform-Specific & Salesforce Developme

Approach

Say who the caller is and what they do when the call fails halfway.
Define the identity of a request so a retry cannot double-apply it.
Separate accepted, pending, failed and confirmed; they are different facts.
Design the error taxonomy before the success shape; callers branch on it.

Follow-up

What happens if the caller retries after a timeout?
How does a client discover it is on an old version of this contract?

What is the role of the Salesforce Sharing Architecture, and how do you enforce field-level security in custom

Medium · Platform-Specific & Salesforce Developme

What is the role of the Salesforce Sharing Architecture, and how do you enforce field-level security in custom code?

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

Walk me through your process for deploying changes across Salesforce sandboxes to production.

Medium · Platform-Specific & Salesforce Developme

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Describe a complex technical bug you encountered in production and how you went about debugging and fixing it.

Medium · Behavioral & Agile Collaboration

Approach

Establish what changed and when, before forming any theory.
Pick a bisection that eliminates candidates whichever way it turns out.
Check the instrumentation before believing the symptom.
Separate the trigger from the cause; the deploy is rarely the bug.

Follow-up

What would you look at first, and what would it rule out?
How would you tell a cause from a coincidence here?

Suggested practice checklist

Built from the rounds and topics Halvik candidates report.

Day 1 — Map the Halvik loop

Write out the reported sequence: Conversational Screening, Technical Evaluation, Comprehensive Panel Interview.
For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.

Deliverable: A one-page map of the 3 reported rounds, with the weakest marked.

Day 2 — Work Web Application Development

Spend the session on Web Application Development, which Halvik candidates report being tested on.
Write one worked example in Web Application Development and time yourself on it.

Deliverable: One timed worked example in Web Application Development.

Day 3 — Work Full-Stack Development

Spend the session on Full-Stack Development, which Halvik candidates report being tested on.
Write one worked example in Full-Stack Development and time yourself on it.

Deliverable: One timed worked example in Full-Stack Development.

Day 4 — Work Backend Development

Spend the session on Backend Development, which Halvik candidates report being tested on.
Write one worked example in Backend Development and time yourself on it.

Deliverable: One timed worked example in Backend Development.

Day 5 — Answer out loud: Web Development & Full-Stack Architecture

Answer aloud, timed: Explain the difference between client-side rendering and server-side rendering, and when you would choose one over the other.
Answer aloud, timed: How do you secure a RESTful API against common vulnerabilities such as SQL injection and Cross-Site Scripting (XSS)?

Deliverable: Spoken answers to 2 reported Web Development & Full-Stack Architecture question(s), under time.

Day 6 — Answer out loud: Systems Engineering & Cloud Infrastructure

Answer aloud, timed: Describe your experience setting up and maintaining CI/CD pipelines using tools like Jenkins, GitLab CI, or GitHub Actions.
Answer aloud, timed: What are the primary benefits of containerization with Docker, and how do you orchestrate containers using Kubernetes?

Deliverable: Spoken answers to 2 reported Systems Engineering & Cloud Infrastructure question(s), under time.

Day 7 — Answer out loud: Platform-Specific & Salesforce Development

Answer aloud, timed: Explain the difference between declarative customization (flows, validation rules) and programmatic customization (Apex, Lightning Web Components) in Salesforce.
Answer aloud, timed: How do you handle governor limits when writing Apex triggers or batch classes?

Deliverable: Spoken answers to 2 reported Platform-Specific & Salesforce Development question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

Describe your experience setting up and maintaining CI/CD pipelines using tools like Jenkins, GitLab CI, or Gi

Medium · Systems Engineering & Cloud Infrastructu

Describe your experience setting up and maintaining CI/CD pipelines using tools like Jenkins, GitLab CI, or GitHub Actions.

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

How do you handle governor limits when writing Apex triggers or batch classes?

Medium · Platform-Specific & Salesforce Developme

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

Tell me about a time when you had to work with a difficult stakeholder or client. How did you resolve the conf

Medium · Behavioral & Agile Collaboration

Tell me about a time when you had to work with a difficult stakeholder or client. How did you resolve the conflict?

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

Describe a situation where you had to quickly learn a new technology or framework to deliver a project.

Medium · Behavioral & Agile Collaboration

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

How do you estimate your tasks during sprint planning, and what do you do if you realize you cannot meet a dea

Medium · Behavioral & Agile Collaboration

How do you estimate your tasks during sprint planning, and what do you do if you realize you cannot meet a deadline?

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

Walk me through a time when you disagreed with a technical decision made by a team lead or architect. How did

Medium · Behavioral & Agile Collaboration

Walk me through a time when you disagreed with a technical decision made by a team lead or architect. How did you handle it?

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?