A Software Engineer at The Federal National Mortgage Association - Fannie Mae plays a vital role in maintaining the stability and efficiency of the U.S. housing finance system. You will be responsible for designing, developing, and maintaining high-impact software solutions that support mortgage lending, risk management, and large-scale data processing. Your work directly influences how the company manages trillions of dollars in assets, requiring a high degree of precision, scalability, and security. This position is inherently complex, as you will often be working within a large, enterprise-level ecosystem that necessitates a blend of modern cloud architecture and legacy system integration. You will collaborate closely with product managers, data scientists, and cross-functional engineering teams to deliver robust applications. For a Software Engineer, this means balancing the need for rapid feature delivery with the rigorous standards required by a highly regulated financial institution. The environment at is dynamic, where you will tackle challenges involving cloud migration, API development, and data-driven decision-making. You can expect to work on meaningful projects that have a broad scope, requiring you to be both a strong individual contributor and a collaborative team player who can navigate complex technical landscapes. The Federal National Mortgage Association - Fannie Mae
Recruiter Screen
reportedInitial conversation with a recruiter to assess your background and fit for the role.
What to demonstrate
- Initial conversation with a recruiter to assess your background and fit for the role
- Depth in Flask
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 Screening
reportedAssessment of technical skills through coding exercises and technical trivia.
What to demonstrate
- Assessment of technical skills through coding exercises and technical trivia
- Depth in Flask
How to prepare
- Answer aloud and timed: How do you handle REST API design and request handling?
- Answer aloud and timed: Can you explain how you would implement a palindrome method or other basic string manipulation tasks?
Final Round Interviews
reportedMultiple back-to-back interviews focusing on both technical competence and behavioral fit.
What to demonstrate
- Multiple back-to-back interviews focusing on both technical competence and behavioral fit
- Depth in Flask
How to prepare
- Answer aloud and timed: Describe the difference between a list, a dictionary (map), and a tuple in your preferred language.
- Answer aloud and timed: Tell me about a project you worked on and your specific contributions to it.
PracHub editorial advice for the preparation topics above.
Own your resume
Every line on your resume is fair game. If you list a technology, be prepared to answer deep, conceptual questions about how it works under the hood.
Prepare for "Tell me about a time
Have 3–5 stories ready that illustrate your problem-solving, leadership, and conflict-resolution skills. Use the STAR (Situation, Task, Action, Result) method to keep your answers concise.
Research the company
Even if you aren't explicitly asked "What does Fannie Mae do," understanding their role in the mortgage market will help you frame your answers in a way that shows you understand the business context of your code.
Be conversational
The interviewers are looking for a colleague. Treat the interview as a technical discussion between peers rather than an interrogation.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
What are the differences between a compiled and an interpreted language?
What are the differences between a compiled and an interpreted language?
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?
Merge partitioned event streams into one ordered feed with bounded lateness
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
- 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.
- 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.
- 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.
- Handle the idle partition explicitly, because it fails the feed rather than corrupting it: a partition with no traffic never advances its own maximum, so the watermark freezes and output stops entirely. Either every partition emits a periodic idle marker carrying the broker's current time, or the watermark falls back to wall clock for a partition silent beyond a threshold.
Follow-up
- The lateness budget is raised to five minutes. What is the new buffer, and what besides memory changes?
- The consumer restarts. Where does it resume from, and what does the feed look like for the first 30 seconds?
Find overlapping job attempts and peak concurrency from lease records
A day of job_run history yields about 50,000,000 attempt records: (job_run_id, job_type, attempt, started_at, finished_at which is NULL when the worker died, lease_expires_at). Leases expire on a clock, so a job that outran its lease ran twice. Produce (a) every job_run_id whose attempts overlapped in wall-clock time and (b) the peak number of simultaneously running attempts per job_type with the minute it occurred. Target O(n log n). State how you treat a NULL finished_at and what clock skew does to your answer.
Approach
- Define the interval before sorting anything: an attempt occupies [started_at, COALESCE(finished_at, lease_expires_at)). finished_at is observed and lease_expires_at is only a promise, so every attempt without a finish contributes an estimate and the whole result is a lower bound on overlap rather than an exact count.
- For peak concurrency, sweep: emit 2n endpoints, sort by (timestamp, kind) with ends ordered before starts at equal timestamps, then walk the sequence maintaining a counter per job_type and record each type's maximum with its timestamp. O(n log n) dominated by the sort, O(n) space, or O(1) extra if the sort is external and the walk streams.
- For overlap detection, do not compare attempts pairwise. A single global sort by (job_run_id, started_at) gives both the grouping and the order; within a group, keep the maximum end seen so far and report an overlap exactly when the next start is less than that running maximum, which is one linear pass after the sort.
- Half-open intervals matter and are easy to get wrong: with closed intervals an attempt ending at the same millisecond another begins reads as concurrency two, and across 50,000,000 records that artefact swamps the real signal.
Follow-up
- A handler is not idempotent and you have found 400 overlapping jobs. Which of them actually caused damage, and what would you query to find out?
- Peak concurrency for one job_type is 4 against a configured cap of 4. Is the cap working, or is the data hiding attempts that never started?
Find version gaps and relay lag with window functions
outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.
Approach
- Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
- Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
- Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
- Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.
Follow-up
- Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
- Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?
Replace offset paging on the resource feed with keyset
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 four pillars of Object-Oriented Programming (OOP).
Explain the four pillars of Object-Oriented Programming (OOP).
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 handle REST API design and request handling?
How do you handle REST API design and request handling?
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?
Can you explain how you would implement a palindrome method or other basic string manipulation tasks?
Can you explain how you would implement a palindrome method or other basic string manipulation tasks?
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 the difference between a list, a dictionary (map), and a tuple in your preferred language.
Describe the difference between a list, a dictionary (map), and a tuple in your preferred language.
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 would you design a scalable API for a mortgage application processing system?
How would you design a scalable API for a mortgage application processing system?
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?
If you were tasked with migrating a legacy service to the cloud, what steps would you take?
If you were tasked with migrating a legacy service to the cloud, what steps would you take?
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?
Solve this riddle or logic-based problem (these are occasionally used to test lateral thinking).
Solve this riddle or logic-based problem (these are occasionally used to test lateral thinking).
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 approach to debugging a complex production issue.
Walk me through your approach to debugging a complex production issue.
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 The Federal National Mortgage Association - Fannie Mae candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the The Federal National Mortgage Association - Fannie Mae loop
- Write out the reported sequence: Recruiter Screen, Technical Screening, Final Round Interviews.
- 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 Flask
- Spend the session on Flask, which The Federal National Mortgage Association - Fannie Mae candidates report being tested on.
- Write one worked example in Flask and time yourself on it.
Deliverable: One timed worked example in Flask.
03Work REST API Design
- Spend the session on REST API Design, which The Federal National Mortgage Association - Fannie Mae candidates report being tested on.
- Write one worked example in REST API Design and time yourself on it.
Deliverable: One timed worked example in REST API Design.
04Work API Development
- Spend the session on API Development, which The Federal National Mortgage Association - Fannie Mae candidates report being tested on.
- Write one worked example in API Development and time yourself on it.
Deliverable: One timed worked example in API Development.
05Answer out loud: Technical and Domain Knowledge
- Answer aloud, timed: Explain the four pillars of Object-Oriented Programming (OOP).
- Answer aloud, timed: What are the differences between a compiled and an interpreted language?
Deliverable: Spoken answers to 2 reported Technical and Domain Knowledge question(s), under time.
06Answer out loud: Behavioral and Leadership
- Answer aloud, timed: Tell me about a project you worked on and your specific contributions to it.
- Answer aloud, timed: Describe a time you had to work with a difficult team member or navigate a disagreement.
Deliverable: Spoken answers to 2 reported Behavioral and Leadership question(s), under time.
07Answer out loud: System Design and Problem Solving
- Answer aloud, timed: How would you design a scalable API for a mortgage application processing system?
- Answer aloud, timed: If you were tasked with migrating a legacy service to the cloud, what steps would you take?
Deliverable: Spoken answers to 2 reported System Design and Problem Solving 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.
Tell me about a project you worked on and your specific contributions to it.
Tell me about a project you worked on and your specific contributions to 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?
Describe a time you had to work with a difficult team member or navigate a disagreement.
Describe a time you had to work with a difficult team member or navigate a 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 handle tight deadlines or shifting project requirements?
How do you handle tight deadlines or shifting project requirements?
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?
What draws you to The Federal National Mortgage Association - Fannie Mae and the housing finance sector?
What draws you to The Federal National Mortgage Association - Fannie Mae and the housing finance sector?
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 learn a new technology quickly to solve a problem.
Describe a situation where you had to learn a new technology quickly to solve a problem.
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
Tell me about a project you worked on and your specific contributions to it.
- 02
Describe a time you had to work with a difficult team member or navigate a disagreement.
- 03
How do you handle tight deadlines or shifting project requirements?
- 04
What draws you to The Federal National Mortgage Association - Fannie Mae and the housing finance sector?
How difficult are the technical interviews?
The difficulty is generally considered average. The focus is less on "trick" coding questions and more on your ability to explain technical concepts and your past project work.
The Federal National Mortgage Association - Fannie Mae Software Engineer candidate reports ↗Should I practice LeetCode?
While you should be prepared for basic algorithmic logic, the interviewers at The Federal National Mortgage Association - Fannie Mae are more likely to ask about your practical experience, design choices, and core language concepts rather than obscure, high-difficulty competitive programming problems.
The Federal National Mortgage Association - Fannie Mae Software Engineer candidate reports ↗What is the typical timeline?
The process usually spans two to four weeks from the initial screen to an offer. However, timelines can vary; stay in regular contact with your recruiter to manage expectations.
The Federal National Mortgage Association - Fannie Mae Software Engineer candidate reports ↗Is the interview process remote or in-person?
The process is often a mix, with initial rounds conducted via video conference and final rounds sometimes held onsite or via a series of virtual panels.
The Federal National Mortgage Association - Fannie Mae Software Engineer candidate reports ↗What topics does The Federal National Mortgage Association - Fannie Mae test in interviews?
The Federal National Mortgage Association - Fannie Mae interviews most often cover Behavioral Interviewing, SQL, Java, Data Analysis, and Problem Solving. The exact emphasis depends on the specific role you apply for.
The Federal National Mortgage Association - Fannie Mae 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.
- 01The Federal National Mortgage Association - Fannie Mae 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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