Aevex Software Engineer Interview Guide

The 60-second brief

As a Software Engineer at Aevex, you play a vital role in developing advanced technological solutions that support U.S. national security, defense, and commercial aviation missions. You will design, build, and integrate critical software for Unmanned Aerial Systems (UAS), embedded flight controls, sensor fusion pipelines, and specialized mission-system tools. Your daily contributions directly impact airborne special mission operations, helping the organization rapidly prototype and deploy reliable hardware-software integrations. The work environment at Aevex combines the fast-paced agility of rapid prototyping with the rigorous demands of aerospace engineering. You will frequently collaborate across disciplines—working side-by-side with GNC (Guidance, Navigation, and Control) teams, electrical engineers, mechanical designers, and upper management.

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

Focus areas

• Embedded software development
• C programming (embedded)
• Sensor fusion

The Aevex interview process

Aevex candidates report 2 rounds over 2-4 weeks. The stages below are what candidates describe, not a published process.

Recruiter Screening

Initial touchpoints with the recruiter to discuss your background and fit for the role.

What to demonstrate

• Initial touchpoints with the recruiter to discuss your background and fit for the role
• Depth in Embedded software development

How to prepare

• Be able to walk your CV end to end in two minutes, and say why this company specifically.
• Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.

Technical Discussions

In-depth technical evaluations with engineering managers to assess your technical competency.

What to demonstrate

• In-depth technical evaluations with engineering managers to assess your technical competency
• Depth in Embedded software development

How to prepare

• Answer aloud and timed: Describe a time when you had to collaborate with a cross-functional team, such as mechanical or electrical engineers, to resolve an integration issue.
• Answer aloud and timed: Why are you interested in joining Aevex to support national security and aviation missions?

Where candidates lose points

Highlight hands-on hardware experience

When discussing past projects, emphasize not just the code you wrote, but how you physically tested it, debugged bus communications, or interfaced with sensors on real hardware.

Emphasize safety and reliability

In aerospace and defense software, failure is not an option. Frame your design and testing decisions around reliability, determinism, and robust error handling.

Prepare behavioral stories about teamwork

Because Aevex relies on tight collaboration between software, GNC, and electrical teams, be ready to share examples of how you successfully resolved cross-functional disagreements or integration blockers.

Brush up on low-level fundamentals

Review pointer arithmetic, memory management, multi-threading primitives, and interrupt service routines in C and C++, as these topics frequently surface in technical evaluations.

Questions & practice

How do you manage real-time performance aspects, such as multi-threading and time synchronization, in custom h

Medium · Technical Domain and Aerospace Systems

How do you manage real-time performance aspects, such as multi-threading and time synchronization, in custom headless embedded devices?

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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?

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?

Diff a projection against the primary without per-row point reads

Hard · reconciliation · range hashing · throttling

The listing projection has drifted and some rows show a stale version. The primary holds 40,000,000 resource rows across 12,000 tenants while serving 1,200 writes and 14,000 reads per second. The obvious repair, reading each resource row and comparing its version against the projection, is correct and would eventually finish. Explain precisely why it is unacceptable here, then give a diff that finds the differing rows, state its complexity, and make it safe to run against a live primary. Replication lag is usually under 100 ms and is not bounded.

Approach

1. Quantify the naive cost rather than calling it slow: 40,000,000 point reads at even 0.5 ms each is over five hours serialised, and the only lever is concurrency, which is exactly what you cannot spend. The primary's pool is sized for the write path, and 40,000,000 random reads evict the buffer cache that sustains the 85 percent cache hit rate, so the audit degrades the system it is auditing.
2. Replace random access with one ordered pass per side. Both sides can be read in (tenant_id, resource_id) order, which is a sequential scan on each and a merge join in O(n) time and O(1) memory. For a dense diff that is the whole answer, and it reads the primary once instead of 40,000,000 times.
3. For the expected sparse case, compare range hashes instead of rows: partition the key space, compute per range an order-independent aggregate over hash(resource_id, version), compare aggregates, and descend only into ranges that differ. With d differing rows and branching factor B, at most d ranges mismatch per level, so the drill-down examines O(d log_B(n/d)) ranges and reads full rows only in mismatching leaves.
4. Aggregate with a sum modulo 2^64 or a multiset hash, never XOR. XOR is order-independent but self-cancelling, so two rows wrong in the same way, or a row duplicated on one side, leave the range aggregate matching and the range is declared clean.

Follow-up

• The diff reports 900 stale rows. How do you decide between patching those rows and rebuilding the projection from resource_revision?
• Same job, but the projection lives in a search index that cannot be scanned in key order. What changes?

Write the update path that detects a concurrent edit

Medium · optimistic concurrency · transactional outbox · audit history

resource carries version INT NOT NULL DEFAULT 1. resource_revision holds revision_id, resource_id, version, actor_user_id, change_kind, patch JSONB, request_id, created_at with UNIQUE (resource_id, version). outbox_event holds aggregate_type, aggregate_id, aggregate_version, event_type, payload, status. A PUT carries the version the client read. Write the exact statements for the single transaction that applies the edit, records the revision and enqueues 'resource.updated', and give the handler's branch on zero affected rows. Then say what PostgreSQL 16 does under READ COMMITTED when two of these updates hit one row at once.

Approach

1. One transaction, three writes, no network call inside it: UPDATE resource SET title = $3, version = version + 1, updated_at = now() WHERE resource_id = $1 AND tenant_id = $4 AND version = $2; then INSERT the resource_revision row at version $2 + 1; then INSERT the outbox_event row at the same aggregate_version. The event goes to a table rather than a broker because no transaction spans both.
2. Branch on the affected-row count before doing anything else. Zero has three causes — stale version, wrong tenant, row gone — so re-read once and map to 409 carrying the current version, or 404 for an id outside the caller's tenant, which also stops the endpoint confirming that another tenant's id exists.
3. State the engine behaviour instead of assuming it. Under READ COMMITTED the second UPDATE blocks on the row lock, and when the first commits PostgreSQL re-evaluates the WHERE clause against the newly committed row, so the version predicate now fails and the statement reports zero rows. Under REPEATABLE READ the identical collision raises SQLSTATE 40001 instead, so the handler must fold both shapes into one conflict response.
4. Keep UNIQUE (resource_id, version) even though the predicate already serialises writers. It is what makes a lost update unwritable if any other path ever reaches the revision table, and it converts a logic bug into 23505 rather than into a silently missing history row.

Follow-up

• A client sends the version it read ten minutes ago and the resource has moved three versions. What is in your 409 so it can resolve the conflict without a full re-fetch?
• Two editors, two disjoint fields, no overlap. Does your answer still refuse the second write, and should it?

Keep soft-deleted accounts from blocking re-registration

Easy · soft delete · unique constraints · engine differences

app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.

Approach

1. Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
2. Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
3. For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
4. State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.

Follow-up

• A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
• How do you honour an erasure request while resource_revision.actor_user_id still references this table?

Can you explain how GPS, inertial navigation, and sensor fusion interact within a real-time software architect

Medium · Technical Domain and Aerospace Systems

Can you explain how GPS, inertial navigation, and sensor fusion interact within a real-time software architecture?

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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 experience do you have with aircraft design and manufacturing processes?

Medium · Technical Domain and Aerospace Systems

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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 approach the full lifecycle of software development, from requirements collection to functional tes

Medium · Software Engineering Fundamentals

How do you approach the full lifecycle of software development, from requirements collection to functional testing and deployment?

Approach

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

Follow-up

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

Can you discuss your proficiency with low-level programming in C and C++ for resource-constrained microcontrol

Medium · Software Engineering Fundamentals

Can you discuss your proficiency with low-level programming in C and C++ for resource-constrained microcontroller systems?

Approach

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

Follow-up

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

What strategies do you use for configuration management and supporting production software builds during field

Medium · Software Engineering Fundamentals

What strategies do you use for configuration management and supporting production software builds during field updates?

Approach

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

Follow-up

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

How do you ensure that proprietary information and critical data remain confidential and secure throughout the

Medium · Software Engineering Fundamentals

How do you ensure that proprietary information and critical data remain confidential and secure throughout the development process?

Approach

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

Follow-up

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

What communication protocols do you rely on most frequently when interfacing with microcontrollers, and how do

Medium · Technical Domain and Aerospace Systems

What communication protocols do you rely on most frequently when interfacing with microcontrollers, and how do you troubleshoot bus-level communication errors?

Approach

1. Establish what changed and when, before forming any theory.
2. Pick a bisection that eliminates candidates whichever way it turns out.
3. Check the instrumentation before believing the symptom.
4. 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 Aevex candidates report.

Day 1 — Map the Aevex loop

• Write out the reported sequence: Recruiter Screening, Technical Discussions.
• 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 2 reported rounds, with the weakest marked.

Day 2 — Work Embedded software development

• Spend the session on Embedded software development, which Aevex candidates report being tested on.
• Write one worked example in Embedded software development and time yourself on it.

Deliverable: One timed worked example in Embedded software development.

Day 3 — Work C programming (embedded)

• Spend the session on C programming (embedded), which Aevex candidates report being tested on.
• Write one worked example in C programming (embedded) and time yourself on it.

Deliverable: One timed worked example in C programming (embedded).

Day 4 — Work Sensor fusion

• Spend the session on Sensor fusion, which Aevex candidates report being tested on.
• Write one worked example in Sensor fusion and time yourself on it.

Deliverable: One timed worked example in Sensor fusion.

Day 5 — Answer out loud: Behavioral and Culture Fit

• Answer aloud, timed: Walk me through your resume and highlight a complex technical project where you had to work independently.
• Answer aloud, timed: How do you handle shifting priorities and tight deadlines in a rapid prototyping environment?

Deliverable: Spoken answers to 2 reported Behavioral and Culture Fit question(s), under time.

Day 6 — Answer out loud: Technical Domain and Aerospace Systems

• Answer aloud, timed: Can you explain how GPS, inertial navigation, and sensor fusion interact within a real-time software architecture?
• Answer aloud, timed: What experience do you have with aircraft design and manufacturing processes?

Deliverable: Spoken answers to 2 reported Technical Domain and Aerospace Systems question(s), under time.

Day 7 — Answer out loud: Software Engineering Fundamentals

• Answer aloud, timed: How do you approach the full lifecycle of software development, from requirements collection to functional testing and deployment?
• Answer aloud, timed: Can you discuss your proficiency with low-level programming in C and C++ for resource-constrained microcontroller systems?

Deliverable: Spoken answers to 2 reported Software Engineering Fundamentals question(s), under time.

Behavioural preparation

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

Walk me through your resume and highlight a complex technical project where you had to work independently.

Medium · Behavioral and Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 shifting priorities and tight deadlines in a rapid prototyping environment?

Medium · Behavioral and Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 time when you had to collaborate with a cross-functional team, such as mechanical or electrical eng

Medium · Behavioral and Culture Fit

Describe a time when you had to collaborate with a cross-functional team, such as mechanical or electrical engineers, to resolve an integration issue.

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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?

Why are you interested in joining Aevex to support national security and aviation missions?

Medium · Behavioral and Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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?