Interview guides · Amentum

Amentum Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at Amentum, you are at the intersection of complex systems engineering and mission-critical software development. Amentum operates in highly specialized sectors—including nuclear, defense, and government services—where the software you build often supports infrastructure that is vital to national security and public safety. Your work ensures that complex systems perform reliably under rigorous conditions, requiring a high degree of technical precision and an understanding of the broader operational context. This role is not merely about writing code; it is about engineering solutions that solve real-world, large-scale problems. You will collaborate with cross-functional teams, including systems engineers, project managers, and technical domain experts, to translate complex requirements into robust, maintainable software.

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

Focus areas

Technical Interview Fundamentals
Problem Solving / Analytical Reasoning
Object-Oriented Programming (OOP)

The Amentum interview process

Amentum candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Recruiter Screening

Initial screening conducted by a recruiter to assess candidate fit for the role.

What to demonstrate

Initial screening conducted by a recruiter to assess candidate fit for the role
Depth in Technical Interview Fundamentals

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

One or more technical interviews with managers and senior engineers to evaluate technical skills.

What to demonstrate

One or more technical interviews with managers and senior engineers to evaluate technical skills
Depth in Technical Interview Fundamentals

How to prepare

Answer aloud and timed: Can you walk us through your process for debugging a complex technical issue?
Answer aloud and timed: Describe your experience with specific software tools relevant to this role (e.g., CAD, FEA, or specific scripting languages).

Previous Work Walkthrough

Candidates may be asked to discuss their previous work experience in detail.

What to demonstrate

Candidates may be asked to discuss their previous work experience in detail
Depth in Technical Interview Fundamentals

How to prepare

Answer aloud and timed: How do you ensure your code is both efficient and maintainable?
Answer aloud and timed: Tell us about a time you had to explain a complex technical concept to a non-technical stakeholder.

Group Task

Participation in a group task to assess collaboration and problem-solving skills.

What to demonstrate

Participation in a group task to assess collaboration and problem-solving skills
Depth in Technical Interview Fundamentals

How to prepare

Answer aloud and timed: How do you handle disagreements regarding technical choices within a project team?
Answer aloud and timed: Describe a situation where you had to adapt to a changing project requirement or deadline.

Real-time Coding Problems

Candidates may solve coding problems in real-time to demonstrate technical proficiency.

What to demonstrate

Candidates may solve coding problems in real-time to demonstrate technical proficiency
Depth in Technical Interview Fundamentals

How to prepare

Answer aloud and timed: Why are you interested in working for Amentum, and how do you see yourself contributing to our mission?
Answer aloud and timed: Tell us about a project you are particularly proud of and the role you played in its success.

Where candidates lose points

Review your resume extensively

You will be asked to explain the technical details of the projects you have listed. Be prepared to talk about your specific contributions and the engineering trade-offs you made.

Practice your "Technical Storytelling

When asked a technical question, don't just provide a one-word answer. Explain your thought process, the alternatives you considered, and why you chose your specific approach.

Dress professionally

Even for virtual interviews, dress as you would for an in-person meeting to show respect for the process and the interviewers.

Prepare questions for the interviewers

Use the time at the end of the interview to ask about their team culture, the biggest technical challenges they are currently facing, or how the team supports professional development.

Questions & practice

How do you approach memory management and pointer logic in languages like C or C++?

Medium · Technical Foundations

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?

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?

Track a rolling failure rate per destination for circuit decisions

Easy · sliding window · ring buffer · circuit breaker

The egress service delivers about 1,500 webhooks per second across roughly 40,000 destinations, each call bounded by a 10 second timeout. Maintain, per destination, the failure rate over the trailing 60 seconds so a caller can ask before dispatch whether the circuit should open. Attempts arrive as (destination_id, finished_at_ms, outcome). Requirement: amortised O(1) per attempt, with total memory bounded by the destination count rather than by traffic. Give the structure, its exact memory, and the rule that stops a destination with three attempts from opening a circuit.

Approach

Name the exact-deque version and then reject it as the default. Holding timestamps and advancing a tail pointer past anything older than now minus 60 seconds is a correct two-pointer window at amortised O(1) per attempt, but its memory tracks in-window traffic, so one destination in a retry storm holds hundreds of thousands of entries while thousands of quiet destinations hold none.
Use a ring of 60 one-second buckets per destination, each bucket a pair of counters for attempts and failures. On an attempt, advance the ring by the elapsed whole seconds, zeroing at most min(elapsed, 60) buckets, then increment the head. That is amortised O(1) with a fixed footprint per destination.
State the footprint: 60 buckets times two 4-byte counters is 480 bytes of payload per destination, so 40,000 destinations is roughly 20 to 25 MB with per-entry overhead, bounded by the catalogue rather than by the rate. The cost is granularity, since the oldest bucket ages out in whole seconds, which is far tighter than the decision needs.
Require a minimum sample before the circuit may open. A destination with three attempts and three failures reads as 100 percent and is not evidence; a floor of roughly 20 attempts in the window makes the ratio meaningful, and below that floor use a run of consecutive failures as the trigger instead.

Follow-up

The fleet is 30 instances and each sees roughly a thirtieth of a destination's traffic. Where does the rate actually live, and what does a per-instance answer get wrong?
A destination answers in 9.5 seconds and succeeds. It is not failing but it is consuming your per-destination concurrency. What signal should open the circuit here?

Stop tag and share joins from fanning out a page

Medium · join fan-out · semi-joins · many-to-many

resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.

Approach

Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.

Follow-up

The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
A resource can be shared with the same user twice under different permissions. Does your count change, and should it?

Replace offset paging on the resource feed with keyset

Easy · keyset pagination · composite index · sort order

resource holds resource_id, tenant_id, owner_user_id, title, body_ref, version, status ('draft','active','archived','deleted'), created_at, updated_at, deleted_at, with an index on (tenant_id, status, updated_at DESC, resource_id DESC). The listing endpoint returns active resources for one tenant, newest update first, 50 per page, today with LIMIT 50 OFFSET n. Tenants reach page 400 and rows are created while they read. Write the keyset query, define what the cursor carries and how it is encoded, and say which part of the index each predicate uses. Assume PostgreSQL 16.

Approach

Name the two failures separately. OFFSET 20000 makes the server produce and discard 20,000 rows, so page cost grows with depth rather than with page size. Independently, any write that changes how many rows sort above the offset moves the window between two fetches, and the direction decides which anomaly you get: an insert lands at the head of updated_at DESC and pushes already-returned rows down past the boundary, so they are returned a second time; a delete above the offset, or a row whose updated_at is bumped above the cursor, pulls rows up and one is never returned at all. Nothing in the response reveals either.
Write the seek: WHERE tenant_id = $1 AND status = 'active' AND (updated_at, resource_id) < ($2, $3) ORDER BY updated_at DESC, resource_id DESC LIMIT 50. The row-value comparison is one index range rather than a disjunction, and both columns are NOT NULL, which is what makes that comparison well defined.
Map each predicate onto the index: tenant_id and status are equality on the leading columns, (updated_at, resource_id) is the range, and the ORDER BY matches the index order so no Sort node appears and the scan stops after 50 rows. The DESC in the definition only matters for mixed directions — a plain ascending btree on the same columns is read backwards for this query.
Put both sort columns in the cursor and nothing the client can tamper with into another tenant: base64 of (updated_at, resource_id), validated server-side, with tenant_id taken from the principal.

Follow-up

The client asks for 'jump to page 400'. What do you offer instead, and what does the honest version cost?
Sort order becomes user-selectable across four columns. How many indexes is that, and which would you refuse to add?

Explain the core principles of Object-Oriented Programming (OOP) and how you apply them in your code.

Medium · Technical Foundations

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?

How do you ensure your code is both efficient and maintainable?

Medium · Technical Foundations

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?

Can you walk us through your process for debugging a complex technical issue?

Medium · Technical Foundations

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 Amentum candidates report.

Day 1 — Map the Amentum loop

Write out the reported sequence: Recruiter Screening, Technical Discussions, Previous Work Walkthrough, Group Task, Real-time Coding Problems.
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 5 reported rounds, with the weakest marked.

Day 2 — Work Technical Interview Fundamentals

Spend the session on Technical Interview Fundamentals, which Amentum candidates report being tested on.
Write one worked example in Technical Interview Fundamentals and time yourself on it.

Deliverable: One timed worked example in Technical Interview Fundamentals.

Day 3 — Work Problem Solving / Analytical Reasoning

Spend the session on Problem Solving / Analytical Reasoning, which Amentum candidates report being tested on.
Write one worked example in Problem Solving / Analytical Reasoning and time yourself on it.

Deliverable: One timed worked example in Problem Solving / Analytical Reasoning.

Day 4 — Work Object-Oriented Programming (OOP)

Spend the session on Object-Oriented Programming (OOP), which Amentum candidates report being tested on.
Write one worked example in Object-Oriented Programming (OOP) and time yourself on it.

Deliverable: One timed worked example in Object-Oriented Programming (OOP).

Day 5 — Answer out loud: Technical Foundations

Answer aloud, timed: Explain the core principles of Object-Oriented Programming (OOP) and how you apply them in your code.
Answer aloud, timed: How do you approach memory management and pointer logic in languages like C or C++?

Deliverable: Spoken answers to 2 reported Technical Foundations question(s), under time.

Day 6 — Answer out loud: Behavioral and Situational

Answer aloud, timed: Tell us about a time you had to explain a complex technical concept to a non-technical stakeholder.
Answer aloud, timed: How do you handle disagreements regarding technical choices within a project team?

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

Day 7 — Dry run for Amentum

Run one full mock under time, then write down the two questions you most want to ask your interviewers.

Deliverable: A completed timed mock and two questions to ask.

Behavioural preparation

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

Describe your experience with specific software tools relevant to this role (e.g., CAD, FEA, or specific scrip

Medium · Technical Foundations

Describe your experience with specific software tools relevant to this role (e.g., CAD, FEA, or specific scripting languages).

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?