Frontier AI Technical Interview Question Bank

Topic tags
Python
Product design

Reported interview periodNov 2025–Jul 2026

Extensible Chat-Room Bots

Refactor a chat room so independent bots can observe messages and emit responses without adding bot-specific branches to the room.

Practice focusChatRoom registers bot services and appends every user and bot message to one ordered log. Requirements - AwayBot : /away <text stores a user's status; later mentions of that user emit AwayBot: <user stepped out (<text ) . - MeetBot : /meet <other records a meeting message and marks both users away as is in a call . - TacoBot : /givetaco <taco-string @user counts taco symbols and tracks each recipient's cumulative total. - A bot response must not cause accidental infinite bot activation.…

Free practice

Topic tags
Concurrency
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodJan 2026–May 2026

Design a team chat product

Design a team chat service with channels, direct messages, threads, reactions, file references, presence, and search.

Practice focusDescribe the client and service APIs, core data model, real-time delivery path, durable storage, indexing, and notification flow. Explain how the system preserves message ordering, supports offline clients, reconnects without losing or duplicating messages, and balances latency against consistency. Include scaling boundaries, partitioning, failure recovery, abuse controls, and the metrics you would monitor. Follow-ups 1. Add organization-wide legal retention and deletion policies. 2.…

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
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
Python
Product design

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026

Compressed Vector Dot Product

Design a compact representation for an integer vector that contains long runs of repeated values, then compute the dot product of two vectors stored in that representation without expanding either vector.

Practice focusUse run-length encoding: each vector is a sequence of (value, run length) pairs. Implement: The two vectors must describe the same logical length. Return 0 for two empty vectors and raise ValueError when their expanded lengths differ. Run lengths are positive integers. Your solution should run in O(len(a) + len(b)) time and use O(1) auxiliary space beyond iterator state. Staged follow-ups 1. Explain when run-length encoding is preferable to a sparse (index, value) representation. 2.…

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
Python
Concurrency
Product design

DatabricksCoding

Talk-through codingNo local grader

Reported interview periodOct 2025

Thread-Safe Channel Chat

Implement an in-memory chat service in which users subscribe to channels, messages are appended to channel histories, and users read messages from their current subscriptions.

Practice focusRequirements - Methods may run concurrently and shared state must be protected explicitly. - Sending appends [channel id, user id, message] even if the sender is not subscribed. - Reading concatenates histories for the user's current subscriptions in sorted channel-id order; each channel remains in send order. - Unsubscribing hides that channel's history from subsequent reads. - Repeated subscribe or unsubscribe operations should be idempotent. - Define the consistency point of each operation and avoid exposing partially written messages.…

Free practice

Topic tags
Storage & state
Product design
Communication

OpenAIBehavioralHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Cross-functional disagreement

Tell one story about a disagreement with a product, research, policy, or operations partner. State the shared goal, the competing constraints, what you changed in your own position, and the decision the group m…

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
Storage & state
Reliability
ML / AI
Product design
Communication

OpenAIHiring managerHalf AI-generated

Discussion / designResponse prompt

Reported interview periodNot available

Product judgment under ambiguity

A team can improve model quality, reduce latency, or make failures easier to understand, but can fund only one this quarter. Choose a direction, state the users and evidence behind it, and define what would inv…

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
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
Python
Data structures
Product design

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Dot product of two long integer vectors

Read a shared length and two integer vectors of that length, then return their dot product as a decimal string. Most entries are zero, so the useful work should follow the non-zero positions rather than the dec…

Practice focusRequirements - Line 1 is the length n ; line 2 holds n integers for the first vector; line 3 holds n integers for the second. - Some inputs carry the two characters backslash and n instead of real line breaks; treat both forms as line separators before parsing. - Multiply matching positions, then add the products. Entries may be negative, so the sum can be negative or zero. - Return the total as a plain decimal string with no padding, no plus sign, and no newline. - Do not print the individual products or the operand vectors.…

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
Concurrency
Reliability
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodApr 2026–Sep 2026

Design a Long-Running Video Generation Platform

Design a service where users submit prompts for video generation. Jobs consume scarce accelerators, may run for minutes, can be cancelled, and must survive worker failure.

Practice focusRequirements - Define APIs for submit, status, progress streaming, cancel, retry, and result retrieval. - Queue and schedule jobs under per-user quotas, priorities, and accelerator constraints. - Use leases or heartbeats so abandoned work becomes recoverable. - Make retries safe, preserve checkpoints, and avoid publishing partial or duplicate results. - Store inputs and outputs securely with retention and content-safety controls. - Provide honest progress despite phases with uncertain duration.…

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

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.…

Public brief

Topic tags
Python
ML / AI
Product design

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Implement Batched Scaled Dot-Product Attention

Implement attention for batched multi-head NumPy arrays on CPU. Inputs are finite arrays with the same floating-point dtype; dimensions are positive.

Practice focusShapes are q: (B, H, Tq, Dk) , k: (B, H, Tk, Dk) , and v: (B, H, Tk, Dv) . Return an array of shape (B, H, Tq, Dv) . When return weights=True , return (output, weights) , with weights of shape (B, H, Tq, Tk) . Requirements - Compute scores as q @ k.transpose(-2, -1) / sqrt(Dk) . - Apply softmax along the key-position dimension. - Support an optional boolean mask broadcastable to the score tensor, where false entries cannot receive probability. - Avoid numerical overflow by using a stable softmax or the framework's stable implementation.…

Public brief

Topic tags
Concurrency
Storage & state
ML / AI
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodOct 2025–Jul 2026

Design a Multi-User AI Assistant

Design the backend for a production chat assistant used concurrently by many customers. It should stream model output, invoke approved tools, preserve conversation state, and remain useful under model or depend…

Practice focusRequirements - Define APIs for creating conversations, sending messages, streaming events, cancelling work, and retrieving history. - Isolate tenants and authorize every history or tool access. - Orchestrate model calls and tool calls with timeouts, retries, idempotency, and bounded loops. - Enforce rate limits, quotas, content policy, and cost budgets. - Store message lineage, model/tool versions, and audit data without leaking sensitive prompts. - Set explicit latency, scale, durability, and availability targets.…

Public brief

Topic tags
Python
Product design

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Infer return types in a tiny generic type system

Implement type substitution for a small language. Types are either atomic names, such as int or generic T, or product types containing an ordered list of child types. A function describes parameter templates an…

Practice focusScenario Implement type substitution for a small language. Types are either atomic names, such as int or generic T , or product types containing an ordered list of child types. A function describes parameter templates and an output-type template. Given concrete argument types, infer the concrete return type. Treat int , float , str , bool , and char as concrete primitives. Any other atomic name in a function template is a generic variable.…

Public brief

Topic tags
Product design
Communication

Hiring manager practiceHiring managerAI-generated

Written response30–45 min

Reported interview periodN/A

Resolve a cross-functional disagreement

Practice turning a research, product, and infrastructure disagreement into an owned decision without flattening the real risks.

Practice focusDisagreement, Decision rights, Cross-functional leadership, Escalation, Communication through a written response exercise.

Public brief

Topic tags
Concurrency
Reliability
Security
Product design

xAISystem designAI-generated

Written response45–60 min

Reported interview periodN/A

Design durable scheduled publishing

A posting product lets an author write now and publish later. Design the path from submission to publication, then keep it correct when authors edit, cancel, and retry while delivery fans out to followers.

Practice focusDurable scheduling, Idempotency, Race conditions, Time zones, Operational telemetry through a written response exercise.