Frontier AI Technical Interview Question Bank

Reported interview periodNov 2025–May 2026

Mine Novel Examples from an Unlabeled Corpus

Design a pipeline that selects rare, useful, and diverse examples from a very large unlabeled text corpus for human labeling.

Practice focusRequirements - Define the downstream task, novelty target, labeling budget, and what counts as success. - Remove unsafe, low-quality, duplicate, and near-duplicate content while tracking provenance. - Represent examples for semantic retrieval and compare distance-to-labeled-data, density, uncertainty, and rule-based signals. - Balance novelty against diversity and relevance so annotators are not flooded with one unusual cluster. - Build a review workflow with sampling, auditability, and feedback from annotators.…

Free practice

Topic tags
Data structures
ML / AI
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodNov 2025–Mar 2026

Design an Enterprise Retrieval Chat System

Design a multi-tenant assistant that answers employees' questions from their organization's private documents and cites the passages supporting each answer.

Practice focusRequirements - Cover document ingestion, parsing, chunking, embedding, indexing, retrieval, reranking, generation, and citations. - Enforce document permissions at retrieval time, including group changes and revoked access. - Refresh changed documents without serving mixed or stale versions longer than a defined bound. - Isolate tenants, encrypt sensitive data, and make access auditable. - Handle empty, conflicting, stale, or low-confidence retrieval without inventing an answer.…

Free practice

Topic tags
Data structures
ML / AI

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodJan 2026–Mar 2026

Design retrieval and ranking for a knowledge assistant

Design the retrieval and ranking system for an assistant that answers questions over a large, frequently updated document collection. The system must return relevant supporting passages with low interactive lat…

Practice focusScenario Design the retrieval and ranking system for an assistant that answers questions over a large, frequently updated document collection. The system must return relevant supporting passages with low interactive latency and provide enough evidence for the answer to be inspected. Assume tens of millions of passages, multiple languages, access-controlled documents, and a stream of new or edited content. Goals - Retrieve relevant passages for both keyword-heavy and semantic queries.…

Free practice

Topic tags
Reliability
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodJan 2026

Design a Shared Calendar Service

Design a calendar system where users create events, invite attendees, view free/busy availability, receive reminders, and edit recurring series across time zones.

Practice focusRequirements - Define APIs and storage for calendars, events, attendees, recurrence rules, exceptions, and reminders. - Represent instants and display time zones correctly across daylight-saving transitions. - Support editing an entire series, one instance, or this-and-future instances. - Resolve concurrent edits and preserve an auditable revision history. - Compute free/busy efficiently for users with many calendars and access restrictions. - Deliver reminders reliably without sending duplicates.…

Free practice

Topic tags
Reliability

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodJan 2026

Design a URL Shortening Service

Design a service that creates durable short links and resolves them with low latency under a read-heavy workload.

Practice focusRequirements - Define create, resolve, custom-alias, delete, and analytics APIs. - Generate compact identifiers with low collision risk and no single hot coordinator at target scale. - Preserve custom-alias uniqueness under concurrent requests. - Support expiry, abuse prevention, and safe-link checks. - Cache popular redirects without serving deleted or changed mappings indefinitely. - State traffic, data-retention, latency, and availability assumptions.…

Free practice

Topic tags
Networking
Reliability
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodNov 2025

Design a reliable webhook delivery platform

Design a multi-tenant service that delivers customer events to externally managed HTTP endpoints. Customer endpoints may be slow, unavailable for hours, or return ambiguous failures. The platform must protect i…

Practice focusScenario Design a multi-tenant service that delivers customer events to externally managed HTTP endpoints. Customer endpoints may be slow, unavailable for hours, or return ambiguous failures. The platform must protect its own availability while giving customers secure, observable, and replayable delivery. Assume high sustained event volume, bursty tenants, multiple endpoints per tenant, and payloads that must be delivered in order for some event streams. Functional requirements - Register, verify, rotate secrets for, pause, and delete webhook endpoints.…

Free practice

Topic tags
ML / AI

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodOct 2025

Design a Hosted Model Playground

Design a web application where users enter a prompt, adjust generation parameters, and receive a streamed completion from one of several hosted models.

Practice focusRequirements - Define APIs for generation, streaming, cancellation, model discovery, and saved presets. - Validate parameter ranges and enforce per-user rate, token, and spend limits. - Route to model backends with timeouts, retries, load shedding, and clear partial-failure behavior. - Protect against abuse while preserving prompt privacy and configurable data retention. - Record enough metadata for latency, quality, and cost analysis without exposing sensitive content. - Support experiments that compare two models or configurations fairly.…

Free practice

Topic tags
Data / SQL

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodOct 2025

Design a nearby-places search service

Design a consumer service that returns nearby businesses with ratings, opening hours, and recent reviews. A user supplies a location, an optional query or category, and filters such as “open now.” Results shoul…

Practice focusScenario Design a consumer service that returns nearby businesses with ratings, opening hours, and recent reviews. A user supplies a location, an optional query or category, and filters such as “open now.” Results should feel fresh and should rank useful places ahead of merely close places. Assume a metropolitan launch with tens of millions of businesses globally, high read traffic, and continuous updates from business owners and reviewers. Core requirements - Search by latitude/longitude and radius, optionally constrained by text or category.…

Free practice

Topic tags
Storage & state

AnthropicSystem designAI-generated

Discussion / designResponse prompt

Reported interview periodNot available

A note two people share

Two people edit one note and both need to see the last line that was saved.

Practice focusSystem design round. Two people share one note. Say where the note is stored. Say what both people see when they save the same line. Say what the second person sees when their save does not land. Stop when a third person can only read.

Free practice

Topic tags
Storage & state

AnthropicSystem design

Discussion / designResponse prompt

Reported interview periodNot available

Shared scratch pad

Two people edit one note and need to see who wrote the last line.

Practice focusSystem design round. Two people share one scratch pad during a review. Start by listing what must be true: neither person loses a line, and both can point at who wrote the last line. Place the note in one store and give each save a version. Walk the case where both save the same version. Then the network drops the second save: the first person must not think the second line landed. Then add a third reader who only watches. Say what that reader sees, what you store, and what you would not build for a note this small.

Free practice

Topic tags
Storage & state

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodNot available

Shared scratch pad

Two people edit one note and need to see who wrote the last line.

Practice focusSystem design round. Two people share one scratch pad during a review. Start by listing what must be true: neither person loses a line, and both can point at who wrote the last line. Place the note in one store and give each save a version. Walk the case where both save the same version. Then the network drops the second save: the first person must not think the second line landed. Then add a third reader who only watches. Say what that reader sees, what you store, and what you would not build for a note this small.

Free practice

Topic tags
Storage & state

xAISystem design

Discussion / designResponse prompt

Reported interview periodNot available

Shared scratch pad

Two people edit one note and need to see who wrote the last line.

Practice focusSystem design round. Two people share one scratch pad during a review. Start by listing what must be true: neither person loses a line, and both can point at who wrote the last line. Place the note in one store and give each save a version. Walk the case where both save the same version. Then the network drops the second save: the first person must not think the second line landed. Then add a third reader who only watches. Say what that reader sees, what you store, and what you would not build for a note this small.

Free practice

xAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Disk-backed map

Build a map whose values survive a process crash. A memory-only map does not meet the contract.

Practice focusget returns the stored value or nothing. put stores a pair and must reach disk before it returns. Startup reads the file and rebuilds the map. A torn or partial final line is ignored. Requirements - Part one is an append-only log. Each put adds one line. Startup replays the file. Never rewrite a line in place. - An update of an existing key appends a newer line. Replay keeps the last complete line for that key. - A second process that opens the same path must see committed values. - Part two is compaction.…

Free practice

Topic tags
Data structures

xAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Compressed prefix tree

Store sequences of integers so a shared beginning occupies one path. A plain trie uses one node per integer. Here, a run of nodes that each have only one child is stored as one edge.

Practice focusRequirements - Insert shares an edge when two sequences start the same way. A sequence with nothing in common gets its own branch. - Inserting a shorter sequence after a longer one must cut the long edge. - To cut an edge, walk until the new sequence disagrees. The shared head stays on the parent edge. The old tail becomes one child. The new tail becomes another. - A disagreement on the first integer splits that edge into a one-integer head plus two children. - Exact membership is true only for a sequence that was inserted, not for a proper head of one.…

Free practice

xAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Long video agent pipeline

Sketch a pipeline that turns a script into shots, frames, audio, and a cut. Name which agent owns each stage. The hard part is consistency: characters, places, and props must hold across many scenes. Pacing is …

Practice focusRequirements - Use a scene record, character sheets, and a continuity tracker as shared memory. - Split the work into a director that turns a script into a shot list, a continuity agent that keeps a vector per character and prop, a renderer that calls a video model conditioned on both, and an editor that reviews cuts and pace. - Inside one clip, rely on the video model to keep a subject that leaves and re-enters the frame. Do not rebuild that part.…

Free practice

Topic tags
Algorithms
Product design

xAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Split matrix product

Compute the product of two matrices on a group of devices, two ways, and compare both results with a product computed on one device.

Practice focusRequirements - The device count divides both dimensions. One device is the local product. - Data-parallel: each device multiplies its row slice of the left matrix by the full right matrix and sends that block to rank zero, which stacks the rows. - Sharded: the left matrix is split by rows and the right matrix by columns. Over as many rounds as there are devices, each device passes its right-hand shard to the neighbor and adds that partial into the matching columns of the piece it keeps. - The communicator is a set of blocking queues.…

Free practice

Topic tags
Reliability
Product design

OpenAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Tool execution platform

Design a platform where an AI assistant invokes approved tools on behalf of users. Include tool registration, argument validation, identity and consent, isolated execution, timeouts, idempotency, audit logs, an…

Practice focusPreparation - Write the user or stakeholder, the constraint, and the decision in one sentence each. - Choose one measurement or observable fact that can support the answer. - Name one alternative and the reason it was not selected. Review checklist 1. Did I state the concrete constraint before describing the solution? 2. Did I separate my own decision and work from the team's work? 3. Did I name evidence or a measurement rather than relying on confidence? 4. Can I answer every follow-up without changing the original facts? Staged follow-ups 1.…

Free practice

Topic tags
Data structures
ML / AI
Communication

xAISystem designHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Real-time inference gateway

Design a gateway for low-latency model inference across several model versions and accelerator pools. Include admission control, routing, batching, deadlines, retries, overload behavior, observability, and safe…

Practice focusPreparation - Write the user or stakeholder, the constraint, and the decision in one sentence each. - Choose one measurement or observable fact that can support the answer. - Name one alternative and the reason it was not selected. Review checklist 1. Did I state the concrete constraint before describing the solution? 2. Did I separate my own decision and work from the team's work? 3. Did I name evidence or a measurement rather than relying on confidence? 4. Can I answer every follow-up without changing the original facts? Staged follow-ups 1.…

New public brief

Topic tags
Storage & state
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodSep 2026

Design real-time device monitoring and control

Design a service that ingests telemetry from many devices, detects meaningful state changes, and triggers control actions according to configurable rules.

Practice focusCover the ingestion API, event schema, message transport, stream processing, state storage, rule evaluation, and command-delivery path. Explain how the system handles bursty traffic, duplicate and out-of-order events, intermittent device connectivity, failed control commands, and service recovery. Define the latency and consistency guarantees you would offer, the metrics needed to operate the system, and the safeguards that prevent unstable feedback loops. Follow-ups 1. Support devices that remain offline for days and later upload buffered telemetry. 2.…

Public brief

Topic tags
Storage & state
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodFeb 2026–Sep 2026

Design a browser IDE for many users

Design a browser-based development environment where users can open persistent workspaces, edit files, run programs, and interact with a live terminal.

Practice focusCover workspace storage, process isolation, scheduling, standard-output streaming, terminal input, reconnect after refresh, dependency setup, and file synchronization. Explain how you prevent one user’s code from affecting another user or the host system. Address cold-start latency, idle-workspace suspension, resource quotas, long-running jobs, failure recovery, observability, and the trade-off between warm capacity and infrastructure cost. Follow-ups 1. Support collaborative editing without coupling file consistency to terminal I/O. 2.…

Public brief

Topic tags
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodJan 2026–Sep 2026

Design hold-then-charge payments

Design a payment platform with two operations:

Practice focus- hold synchronously requests authorization from a downstream card network and must return approval or rejection within a 500 ms p95 target. - charge references an approved hold, durably records the request, acknowledges it, and includes it in a later settlement batch. Assume 10 million holds and 8 million charges per day, peaks near 300 requests per second, 5–10 downstream networks, a two-hour nightly settlement window, and a seven-day hold lifetime.…

Public brief

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodApr 2026–Aug 2026

Design Photo Sharing with Content Deduplication

Design a photo-sharing service where users upload images, view their libraries, and share content. Identical bytes should be stored once, while near-duplicate detection may assist organization or moderation.

Practice focusRequirements - Define upload, finalize, view, share, and delete APIs. - Hash content during upload and map user-owned logical objects to immutable blobs. - Preserve authorization: discovering that another user uploaded the same bytes must not leak their identity or metadata. - Make concurrent identical uploads safe and avoid duplicate blob writes. - Delete a blob only after no authorized logical object references it, including delayed or failed workflows.…

Public brief

Topic tags
Algorithms
Data structures

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodJan 2026–Aug 2026

Crossword Constraint Solver

Given a crossword grid, a set of across/down clue entries, and candidate words for each clue, fill the grid so every entry uses one candidate and all crossing letters agree.

Practice focusRequirements - Define data structures for grid cells, clue slots, candidate domains, and crossing constraints. - Return one valid completed grid or report that none exists. - Use constraint propagation and backtracking rather than enumerating every combination. - Choose a search order such as minimum remaining values, and explain tie-breaking. - Restore domains correctly after a failed branch. - Handle prefilled letters, duplicate candidate words, disconnected regions, and ambiguous puzzles.…

Public brief

Topic tags
ML / AI
Product design
Communication

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodAug 2026

Design an interactive model-backed product feature

A collaborative writing product wants an assistant that can transform a selected passage according to a user instruction. The interaction should feel immediate, stream useful output, preserve user control, and …

Practice focusScenario A collaborative writing product wants an assistant that can transform a selected passage according to a user instruction. The interaction should feel immediate, stream useful output, preserve user control, and remain dependable when the model is slow, unavailable, or returns unsafe content. Design the feature from the client interaction through model serving and operational controls. Product requirements - Start visible progress quickly and stream partial output when possible.…