The Swan Food · Software Engineer
Updated · 2026-10-02

The Swan Food Software Engineer
Interview Guide

THE 60-SECOND BRIEF

At The Swan Food, a Software Engineer is a vital driver of the digital experiences that connect customers with high-quality food solutions. You will be responsible for building, scaling, and maintaining the core web applications and backend services that power our operations. From optimizing user-facing interfaces to architecting robust systems that handle real-time transactions, your work directly influences how users interact with our brand and how efficiently our internal teams operate. This role requires a balance of frontend precision and backend stability. You will not just write code; you will solve complex logistical and user-experience challenges in a fast-paced environment.

This guide is scoped to a Software Engineer candidate at The Swan Food.

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

JavaScriptCSSFront-end Web Fundamentals

25 min read

Browse Software Engineer questions

See the practice prompts

20Practice promptsAcross five skill areas

At The Swan Food, a Software Engineer is a vital driver of the digital experiences that connect customers with high-quality food solutions. You will be responsible for building, scaling, and maintaining the core web applications and backend services that power our operations. From optimizing user-facing interfaces to architecting robust systems that handle real-time transactions, your work directly influences how users interact with our brand and how efficiently our internal teams operate. This role requires a balance of frontend precision and backend stability. You will not just write code; you will solve complex logistical and user-experience challenges in a fast-paced environment. Whether you are refactoring legacy interfaces into modern component-based architectures or designing scalable APIs, your contributions will ensure that The Swan Food remains a highly competitive and reliable service. To succeed as a Software Engineer here, you must possess strong technical fundamentals, a passion for clean code, and a pragmatic approach to problem-solving. We look for engineers who take extreme ownership of their code, from the initial architectural design to deployment and post-launch optimization.

01

Recruiter Conversation

reported

Initial conversation with a recruiter to discuss your background and expectations.

What to demonstrate

  • Initial conversation with a recruiter to discuss your background and expectations
  • Depth in JavaScript

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.
The Swan Food Software Engineer candidate reports ↗
02

Technical Screening Call

reported

Technical screening call with an engineering lead to discuss past projects and answer foundational technical questions.

What to demonstrate

  • Technical screening call with an engineering lead to discuss past projects and answer foundational technical questions
  • Depth in JavaScript

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.
The Swan Food Software Engineer candidate reports ↗
03

Take-Home Assignment

reported

Completion of a take-home technical assignment within a specified timeframe.

What to demonstrate

  • Completion of a take-home technical assignment within a specified timeframe
  • Depth in JavaScript

How to prepare

  • Answer aloud and timed: Describe the lifecycle hooks of a modern frontend framework (such as Angular or React) and when to use them.
  • Answer aloud and timed: How would you design a RESTful API to handle real-time order tracking?
The Swan Food Software Engineer candidate reports ↗
04

Deep-Dive Technical Interview

reported

Review of the take-home task and discussion of system architecture.

What to demonstrate

  • Review of the take-home task and discussion of system architecture
  • Depth in JavaScript

How to prepare

  • Answer aloud and timed: Explain the difference between camelCase and snake_case naming conventions, and why consistency matters across database schemas and API payloads.
  • Answer aloud and timed: How do you handle database migrations in a production environment without causing downtime?
The Swan Food Software Engineer candidate reports ↗
05

Culture Fit Conversation

reported

Conversation with a founder or engineering director to evaluate cultural alignment.

What to demonstrate

  • Conversation with a founder or engineering director to evaluate cultural alignment
  • Depth in JavaScript

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 culture fit conversation above and write down what you would ask to confirm before it.
The Swan Food Software Engineer candidate reports ↗

PracHub editorial advice for the preparation topics above.

01

Review your take-home task carefully before the technical interview

Be prepared to defend your architectural choices, explain how you would scale your solution, and discuss any trade-offs you made due to time constraints.

02

Don't ignore the fundamentals

While frameworks are important, we place a high value on core JavaScript, HTML, and CSS knowledge. Make sure you can write clean, framework-agnostic code.

03

Hardcoding to the sample inputs

Solve the stated problem rather than the two examples; special-casing a literal to make a sample pass is obvious immediately and reads as either a misunderstanding or an attempt to fake progress. If you genuinely cannot generalise yet, say which part is a stub and what would replace it.

Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.

17 technical prompts0 include a worked solution

Track a rolling failure rate per destination for circuit decisions

easy
sliding windowring buffercircuit 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
  1. 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.
  2. 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.
  3. 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.
  4. 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?

Find overlapping job attempts and peak concurrency from lease records

medium
sweep lineintervalsleases

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
  1. 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.
  2. 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.
  3. 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.
  4. 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?

Canonicalise a request body into a stable idempotency fingerprint

medium
parsingcanonicalisationhashing

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
  1. 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.
  2. 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.
  3. 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.
  4. 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?

Built from the rounds and topics The Swan Food candidates report.

Small steps. Visible outcomes.0 / 7 completed
ONE WEEK · YOUR PACE

Prepare, practise & reflect

One practical outcome each day. Spend longer where you need it.

0 / 7 done
01Map the The Swan Food loop
  • Write out the reported sequence: Recruiter Conversation, Technical Screening Call, Take-Home Assignment, Deep-Dive Technical Interview, Culture Fit Conversation.
  • 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.

02Work JavaScript
  • Spend the session on JavaScript, which The Swan Food candidates report being tested on.
  • Write one worked example in JavaScript and time yourself on it.

Deliverable: One timed worked example in JavaScript.

03Work CSS
  • Spend the session on CSS, which The Swan Food candidates report being tested on.
  • Write one worked example in CSS and time yourself on it.

Deliverable: One timed worked example in CSS.

04Work Front-end Web Fundamentals
  • Spend the session on Front-end Web Fundamentals, which The Swan Food candidates report being tested on.
  • Write one worked example in Front-end Web Fundamentals and time yourself on it.

Deliverable: One timed worked example in Front-end Web Fundamentals.

05Answer out loud: Frontend & Web Standards
  • Answer aloud, timed: Explain the difference between absolute, relative, and fixed positioning in CSS.
  • Answer aloud, timed: How do you optimize a web application's loading performance when dealing with large media assets?

Deliverable: Spoken answers to 2 reported Frontend & Web Standards question(s), under time.

06Answer out loud: Backend Architecture & Logic
  • Answer aloud, timed: How would you design a RESTful API to handle real-time order tracking?
  • Answer aloud, timed: Explain the difference between camelCase and snake_case naming conventions, and why consistency matters across database schemas and API payloads.

Deliverable: Spoken answers to 2 reported Backend Architecture & Logic question(s), under time.

07Answer out loud: System Design & Scenario-Based
  • Answer aloud, timed: How would you structure a multi-tenant web application to ensure data isolation?
  • Answer aloud, timed: Describe how you would handle a sudden spike in traffic on our checkout service.

Deliverable: Spoken answers to 2 reported System Design & Scenario-Based 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.

How do you handle database migrations in a production environment without causing downtime?

medium
Backend Architecture & Logic

How do you handle database migrations in a production environment without causing downtime?

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?

Turn a code review disagreement into a decision

easy
code reviewoptimistic concurrencycommunication

A colleague's change updates a row with UPDATE resource SET version = version + 1 WHERE resource_id = $1 AND version = $2 and treats an affected-row count of zero as a successful no-op. You read that as a silently lost update; they think returning 200 is friendlier to clients than returning a conflict. Describe how you have handled a review disagreement of this shape: what goes in the comment, when you leave the thread, and who decides. Then write the comment you would leave here, in under 80 words.

Approach
  1. Sort the disagreement before writing anything. A silently discarded write is a correctness claim about data; the choice between 409 and 412 is taste. Only the first justifies blocking a merge, and saying which one you are doing is most of the value of the comment.
  2. Make the claim reproducible in the comment itself with an interleaving rather than a principle: A reads version 7, B reads version 7, B commits version 8, A's predicate matches zero rows, A is told it succeeded and A's edit is gone.
  3. Offer the alternative with its cost attached: return 409 carrying the current version and the revision that won, so the client can re-read and re-apply. Note that automatic retry is not the fix, because a retry re-reads the winner's state and reapplies an intent formed against data that no longer exists.
  4. Apply an escalation rule you can state: two round trips on the thread, then a call, and the service's owner decides rather than the reviewer. A reviewer who cannot be overruled is a bottleneck with extra steps.
Follow-up
  • Where would you put the test that fails if someone reintroduces the swallowed zero rowcount?
  • The author says clients cannot handle a 409. How do you check whether that is true?

Ship under a deadline and bound the debt you chose

medium
paginationtechnical debttradeoffs

You have four days to ship a tenant-facing listing endpoint. The version you would defend uses keyset pagination over (tenant_id, status, updated_at DESC, resource_id DESC); the version you can finish uses LIMIT/OFFSET with no matching index. Describe a deadline call you actually made of this shape: what you shipped, what you knowingly deferred, how you bounded the damage with a mechanism rather than an intention, and the specific numeric condition that would force the follow-up. Name who you told and where you wrote it down.

Approach
  1. Name the deferred failure precisely instead of calling it slow. OFFSET n makes the database produce and discard n rows, so cost grows with page depth; without an index matching the sort, every matching row is read and sorted before the limit applies; and rows inserted between two page fetches shift across the boundary so items are skipped or repeated with nothing in the response to signal it.
  2. Bound the blast radius with something mechanical rather than a promise: cap maximum page depth, cap page size, restrict the endpoint to one internal caller, or keep it behind a flag. State which failure each cap removes and which it leaves standing.
  3. Attach a number to the trigger and wire it to an alarm: the first tenant crossing N resources, or the endpoint's p99 crossing its share of the 400 ms budget, so the debt announces itself instead of waiting to be remembered.
  4. Write it where the next engineer looks, which is the code and the ticket, not a chat message: what was deferred, why, the cap, and the trigger.
Follow-up
  • At what page depth does the offset version breach your latency budget, given your page size and row counts?
  • What breaks first when you switch to keyset pagination later, and what does a client holding an old page token see?
  • 01

    How do you handle database migrations in a production environment without causing downtime?

  • 02

    A colleague's change updates a row with UPDATE resource SET version = version + 1 WHERE resource_id = $1 AND version = $2 and treats an affected-row count of zero as a successful no-op. You read that as a silently lost update; they think returning 200 is friendlier to clients than returning a conflict. Describe how you have handled a review disagreement of this shape: what goes in the comment, when you leave the thread, and who decides. Then write the comment you would leave here, in under 80 words.

  • 03

    You have four days to ship a tenant-facing listing endpoint. The version you would defend uses keyset pagination over (tenant_id, status, updated_at DESC, resource_id DESC); the version you can finish uses LIMIT/OFFSET with no matching index. Describe a deadline call you actually made of this shape: what you shipped, what you knowingly deferred, how you bounded the damage with a mechanism rather than an intention, and the specific numeric condition that would force the follow-up. Name who you told and where you wrote it down.

PracHub preparation framework ↗
How long do I have to complete the take-home task?

We typically give candidates 48 hours to complete the assignment once it is sent. However, we highly recommend planning your time carefully to ensure you can deliver a high-quality, fully-tested solution without rushing.

The Swan Food Software Engineer candidate reports ↗
What stack is used at The Swan Food?

Our stack is primarily built on JavaScript/TypeScript, modern frontend frameworks, and a mix of Node.js and Java on the backend. We value engineers who are adaptable and can work across different parts of the stack as needed.

The Swan Food Software Engineer candidate reports ↗
How technical is the final interview with the founder?

The final interview is focused primarily on culture fit, your career goals, and your alignment with our company values. While there may be light technical discussions, it is mostly a casual conversation to ensure we are a good match for each other.

The Swan Food Software Engineer candidate reports ↗
What is the hybrid work policy?

We offer a flexible hybrid work model depending on your location. Specific details regarding in-office expectations will be discussed during your initial call with the recruiter.

The Swan Food Software Engineer candidate reports ↗
What topics does The Swan Food test in interviews?

The Swan Food interviews most often cover JavaScript, CSS, AngularJS, Communication Skills, and Project Management. The exact emphasis depends on the specific role you apply for.

The Swan Food 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.