At MDA, a Software Engineer is at the forefront of space technology, contributing to complex, mission-critical systems that operate in some of the most challenging environments imaginable. Whether you are working on Synthetic Aperture Radar (SAR) payloads or digital payload systems, your code and designs directly influence the capability of satellites to observe, track, and analyze our planet. This role is not just about writing software; it is about engineering reliability into systems where failure is not an option. You will join teams that blend cutting-edge software development with high-level systems engineering. Your work will bridge the gap between abstract requirements and the physical reality of space-borne hardware. The complexity of the projects—ranging from signal processing to payload control—demands a rigorous analytical mindset, a deep commitment to precision, and the ability to thrive in a highly collaborative, interdisciplinary environment.
Technical Screening
reportedInitial assessment to establish baseline skills relevant to the position.
What to demonstrate
- Initial assessment to establish baseline skills relevant to the position
- Depth in Synthetic Aperture Radar (SAR)
How to prepare
- Answer aloud and timed: How do you approach debugging a system where software and hardware components are tightly coupled?
- Answer aloud and timed: Explain the role of signal processing in a Synthetic Aperture Radar system.
Technical Assessments
reportedMultiple rounds of deeper technical evaluations to test specific skills.
What to demonstrate
- Multiple rounds of deeper technical evaluations to test specific skills
- Depth in Synthetic Aperture Radar (SAR)
How to prepare
- Answer aloud and timed: How do you ensure real-time performance in a resource-constrained environment?
- Answer aloud and timed: Describe your experience with embedded systems or low-level programming languages.
Behavioral Assessments
reportedEvaluation of candidates' alignment with company culture and values.
What to demonstrate
- Evaluation of candidates' alignment with company culture and values
- Depth in Synthetic Aperture Radar (SAR)
How to prepare
- Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
- Re-read the description of the behavioral assessments above and write down what you would ask to confirm before it.
2 candidate reports. Individual accounts describe a particular role and hiring cycle.
MDA Software Engineer interview with basic Python and disrupted onsite
I began with a short expectation-setting call that felt vague, more like a quick check than a senior-level conversation. I discussed my experience and answered one basic Python question about a list versus a tuple. There was little follow-up about what the role required or what they expected at that level. The next day I went to the Farnborough office for an onsite. The meeting felt chaotic: the…
Read full experienceMDA Software Engineer Interview Experience: Reading and testing Python code
The interview began with a recruiter-style conversation. It included behavioral questions, quick trivia from my CV, and why I was interested in the company. Then it moved to Python. I had to analyze an existing piece of code, explain what it did, and verify it by testing it. After walking through the code's behavior, I ran the tests and explained what I found. The interview was direct. It was les…
Read full experiencePracHub editorial advice for the preparation topics above.
Structure your answers
Use the STAR method (Situation, Task, Action, Result) to keep your behavioral answers concise and impactful.
Show your work
When solving technical problems on a whiteboard or screen, speak your thoughts aloud so the interviewer can follow your logic.
Focus on the "Why
Don't just explain what you did; explain why you chose a particular approach over alternatives.
Prepare questions
At the end of your interview, ask insightful questions about the team's current challenges or the project lifecycle to demonstrate genuine interest.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
How would you handle memory management in a long-running, mission-critical application?
How would you handle memory management in a long-running, mission-critical application?
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?
Collapse a redelivered event batch into per-aggregate high-water marks
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
- 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.
- 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.
- 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.
- 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?
Canonicalise a request body into a stable idempotency fingerprint
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?
Write the update path that detects a concurrent edit
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
- 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.
- 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.
- 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.
- 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?
Stop tag and share joins from fanning out a page
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?
Explain the role of signal processing in a Synthetic Aperture Radar system.
Explain the role of signal processing in a Synthetic Aperture Radar system.
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 real-time performance in a resource-constrained environment?
How do you ensure real-time performance in a resource-constrained environment?
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 translate high-level system requirements into actionable software specifications?
How do you translate high-level system requirements into actionable software specifications?
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 approach testing and validation for systems that cannot be easily accessed after deployment?
How do you approach testing and validation for systems that cannot be easily accessed after deployment?
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?
What strategies do you use to manage technical debt in long-term engineering projects?
What strategies do you use to manage technical debt in long-term engineering projects?
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 approach debugging a system where software and hardware components are tightly coupled?
How do you approach debugging a system where software and hardware components are tightly coupled?
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?
Built from the rounds and topics MDA candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the MDA loop
- Write out the reported sequence: Technical Screening, Technical Assessments, Behavioral Assessments.
- 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.
02Work Synthetic Aperture Radar (SAR)
- Spend the session on Synthetic Aperture Radar (SAR), which MDA candidates report being tested on.
- Write one worked example in Synthetic Aperture Radar (SAR) and time yourself on it.
Deliverable: One timed worked example in Synthetic Aperture Radar (SAR).
03Work SAR Payload Engineering
- Spend the session on SAR Payload Engineering, which MDA candidates report being tested on.
- Write one worked example in SAR Payload Engineering and time yourself on it.
Deliverable: One timed worked example in SAR Payload Engineering.
04Work Digital Payload System Engineering
- Spend the session on Digital Payload System Engineering, which MDA candidates report being tested on.
- Write one worked example in Digital Payload System Engineering and time yourself on it.
Deliverable: One timed worked example in Digital Payload System Engineering.
05Answer out loud: Technical Foundations
- Answer aloud, timed: How do you approach debugging a system where software and hardware components are tightly coupled?
- Answer aloud, timed: Explain the role of signal processing in a Synthetic Aperture Radar system.
Deliverable: Spoken answers to 2 reported Technical Foundations question(s), under time.
06Answer out loud: Systems Thinking and Design
- Answer aloud, timed: How do you translate high-level system requirements into actionable software specifications?
- Answer aloud, timed: Describe a time you had to optimize a system to meet a strict latency or throughput constraint.
Deliverable: Spoken answers to 2 reported Systems Thinking and Design question(s), under time.
07Answer out loud: Behavioral and Professional
- Answer aloud, timed: Describe a time you had to work with a cross-functional team to resolve a technical disagreement.
- Answer aloud, timed: How do you maintain quality standards when working under aggressive project timelines?
Deliverable: Spoken answers to 2 reported Behavioral and Professional question(s), under time.
Expand any day for tasks and deliverables. Your progress is saved on this device.
Behavioural rounds judge the decision you made and what it cost.
Describe your experience with embedded systems or low-level programming languages.
Describe your experience with embedded systems or low-level programming 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?
Describe a time you had to optimize a system to meet a strict latency or throughput constraint.
Describe a time you had to optimize a system to meet a strict latency or throughput constraint.
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 time you had to work with a cross-functional team to resolve a technical disagreement.
Describe a time you had to work with a cross-functional team to resolve a technical disagreement.
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 maintain quality standards when working under aggressive project timelines?
How do you maintain quality standards when working under aggressive project timelines?
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 you identified a critical flaw in a design; how did you communicate and address it?
Tell me about a time you identified a critical flaw in a design; how did you communicate and address 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?
- 01
Describe your experience with embedded systems or low-level programming languages.
- 02
Describe a time you had to optimize a system to meet a strict latency or throughput constraint.
- 03
Describe a time you had to work with a cross-functional team to resolve a technical disagreement.
- 04
How do you maintain quality standards when working under aggressive project timelines?
How much time should I dedicate to preparing for the technical rounds?
Given the specialized nature of the work, you should allocate significant time to reviewing your core technical fundamentals and any specific domain knowledge mentioned in the job posting. Aim for a focused preparation period of at least two to three weeks.
MDA Software Engineer candidate reports ↗What is the company culture like at MDA?
MDA values technical excellence, collaboration, and a sense of mission. You will find a culture that is professional and highly supportive, where engineers are encouraged to take ownership of their work and contribute to high-impact projects.
MDA Software Engineer candidate reports ↗How can I stand out during the interview process?
You can differentiate yourself by connecting your previous experience to the challenges of space-based systems. Demonstrating an understanding of the trade-offs between performance, reliability, and power consumption will show that you are thinking like an MDA engineer.
MDA Software Engineer candidate reports ↗What topics does MDA test in interviews?
MDA interviews most often cover Engineering Program Management, Systems Engineering, Digital Signal Processing (DSP), Stakeholder Management, and Real-Time Systems. The exact emphasis depends on the specific role you apply for.
MDA Software Engineer candidate reports ↗Sources & methodology 3 sources ↗
No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.
- 01MDA Software Engineer candidate reports ↗
Company-reported rounds, questions and FAQ.
Candidate reports · Accessed 2026-09-22 - 02PracHub Software Engineer practice ↗
PracHub practice material, not company-reported.
PracHub page · Accessed 2026-09-22 - 03PracHub preparation framework ↗
PracHub preparation guidance.
PracHub page · Accessed 2026-09-22
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