Full-stack Engineer Interview Prep & Rubrics

Both ends of the stack at moderate depth, with the integration and API-boundary questions specific to full-stack loops.

The loop, in order

Data Structures & Algorithms44 questions · 16 topicsDSA interview questions organised by tested pattern: arrays, hashing, rotated arrays, dynamic programming, graphs, heaps and sliding windows, so you learn transferable coding-round techniques instead of memorising puzzles.
Frontend Engineering35 questions · 9 topicsBrowser-platform depth, framework reasoning, and the frontend-specific design round that full-stack candidates are least prepared for.
Backend Engineering26 questions · 7 topicsLanguage-agnostic service engineering: the protocols, boundaries, and failure handling that sit between a coding round and a full system design round.
Databases & SQL25 questions · 8 topicsQuery-writing rounds and the storage-engine reasoning behind why a query is slow, for backend, data, and DBA roles alike.
System Design63 questions · 12 topicsOpen-ended design rounds broken into the building blocks they draw on, plus full case studies worked end to end with explicit trade-off reasoning.
Behavioural & Culture Fit21 questions · 8 topicsThe round candidates most often under-prepare, treated as a skill with structure rather than small talk, including the rubric interviewers score against.
HR, Screening & Offer18 questions · 6 topicsThe recruiter and HR rounds that gate the technical loop and decide your compensation, where most candidates improvise and lose money.

Latest for this track

hardScenarioConceptCoding

A modal passed design and QA review, but keyboard users report they can tab out of it into the page behind, and once they do they cannot get back or close it. Diagnose it and tell me what a correct dialog does.

The dialog was built as a styled div, so nothing marks the rest of the page inert. Focus was never moved in, never constrained, never restored on close, and Escape was never wired. A correct dialog moves focus in, keeps it in, restores it, marks background inert and is labelled - which native dialog with showModal gives you almost for free.

Accessibility4 minmid, senior, staff

mediumConceptScenario

A save button calls an API, the request fails, the error appears in the console - and the UI still shows 'Saved'. Walk me through what is actually happening in that promise chain.

A catch handler that returns normally converts a rejected promise into a fulfilled one, so every then after it runs as though nothing failed. Combined with fetch, which only rejects on network errors and resolves happily on a 500, the chain reports success twice over. Fix by re-throwing from catch, checking response.ok, and modelling UI state as a machine.

Javascript Core4 minentry, mid, senior

hardScenarioDesignConcept

A customer reports seeing another company's records in your admin console. Walk me through the first hour, and then tell me what you change so this class of bug cannot happen again.

Treat it as a confirmed breach until proven otherwise: preserve logs, scope who saw what, and start the disclosure clock alongside the investigation. The cause is almost always tenant scoping living in application code, where one forgotten filter leaks everything - so move enforcement below the code, to row-level security.

Security And Multitenancy4 minsenior, lead, staff

mediumCodingConcept

Edit distance where insert costs 1, delete costs 2 and replace costs 3. Define the DP state and the recurrence, and tell me what changes from the classic version.

The state is unchanged - the minimum cost to transform the first i characters of one string into the first j of the other - because the subproblem structure does not depend on what operations cost. Only the recurrence changes, adding a per-operation weight instead of a uniform 1, and the base cases become multiples of the insert and delete costs rather than i and j.

Dynamic Programming4 minmid, senior

mediumConceptDesignScenario

Two clients open the same record, both edit it, and the second save silently overwrites the first. How would you use ETags to turn that lost update into something the client can see and handle?

Return a strong ETag on GET, require If-Match on writes, and reject a stale token with 412 Precondition Failed so a lost update becomes a visible error rather than silent data loss. What makes it correct is that the comparison and the write must be one atomic operation - an UPDATE guarded by the version in its WHERE clause - because a SELECT then UPDATE reintroduces the race.

Http And Rest4 minmid, senior, staff

hardConceptScenarioDesign

Engineers added a user_id label to a few metrics and the observability bill went up tenfold. Explain what actually happened, and how you would fix it without losing the ability to debug.

Every distinct combination of label values is a separate time series with its own index entry, so an unbounded label multiplies series count by the number of users rather than adding one dimension. Metrics are the wrong tool for per-entity questions: keep labels bounded, move per-user debugging to exemplar-linked traces, and guard against the next unbounded label.

Observability At Scale5 minmid, senior, staff