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Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

Company

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Frontier Rehearsal · Independent practice · Not affiliated with OpenAI, Anthropic, or xAI.

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Home
Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

Company

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 46 Coding 36 System design 10 Behavioral 0 Hiring manager 0 Project deep dive 0

Topics

Filter question bank by topic tagsAll 269 Python 161 Algorithms 40 Data structures 46 Concurrency 27 Distributed systems 7 Storage & state 43 Networking 7 Reliability 30 ML / AI 27 Data / SQL 24 Security 7 Product design 25 Communication 66

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

40 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Column order of a binary tree

Rebuild a binary tree from its level-order serialization, then group the node values by column, moving left to right across columns. Inside one column the values should follow the order in which a breadth-first…

Practice focusRequirements - The first line is a level-order serialization separated by commas. A missing child is written as null , and the whole line may optionally be wrapped in square brackets. An empty line or [] means there is no tree. - Children attach in queue order: each non-null node consumes the next two slots as its left child and then its right child. - The root sits in column 0; a left edge shifts the column by -1 and a right edge by +1 . - Emit one inner list per occupied column, ordered from the smallest column offset to the largest.…

Public brief

Topic tags
Python
Data structures
Reliability

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Jun 2026

Design a Type-Safe Durable LRU Cache

Extend a crash-recoverable LRU cache to support built-in containers and explicitly registered domain objects without using unsafe object serialization.

Practice focusRequirements - Produce canonical, type-tagged keys for None , booleans, integers, finite floats, strings, bytes, lists, tuples, dictionaries, sets, frozensets, and registered objects. - Preserve distinctions such as True , 1 , and 1.0 ; make dictionary and set identity independent of iteration order. - Allowlist exact classes through unique stable tags. Never dynamically import a class named by stored data. - Encode and decode cached values through the registry and reject unknown or malformed tags.…

Public brief

Topic tags
Python
Data structures
Data / SQL

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–May 2026

Design a Weighted, Checkpointable Data Batcher

You are training on several named datasets. A registry can open an iterator for a dataset at a supplied item offset. Design a batcher that mixes examples according to positive integer weights and can resume exa…

Practice focusThe supplied registry exposes get iterator(name, offset=0) , returning an iterator beginning at that dataset's zero-based item offset. It does not advance any other dataset. Implement the batcher, not the registry. Requirements - Every full batch contains exactly batch size examples while data remains available. - Allocate the integral share first, then distribute leftover slots using a deterministic largest-remainder carry across batches. - Break ties by the insertion order of weights and emit examples grouped in that same dataset order.…

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

Return the k-th value in descending order from an integer array, treating equal values as separate entries. The input arrives in one of two line layouts.

Practice focusRequirements - Layout A: line one is the element count, line two holds the integers, and line three is k . - Layout B: line one is nums=[3,2,1,5,6,4] and line two is k=2 , with no space before either equals sign. - k is one-based and always lies between 1 and the array length, so k = 1 asks for the maximum and k equal to the length asks for the minimum. - Return the selected value as a decimal string; it is a value, not a position.…

New public brief

Topic tags
Python
Data structures
Communication

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Resumable Iterators

Implement an iterator over a copied list that can serialize its position and later resume at the next not-yet-yielded item. Then compose the same behavior across a sequence of lists.

Practice focusSaved state points to the next item, never the last item returned. A completed iterator restores completed. State must be serializable and restoration must not repeat or skip values. The chain state records both the current group and the position within it. Use exactly {"index": integer} for list state and {"outer": integer, "inner": {"index": integer}} for chain state. Reject malformed keys, booleans/nonintegers and negative or out-of-range active indices with ValueError .…

New public brief

Topic tags
Python
Data structures
Storage & state
Networking

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Token-Bucket State Transitions

Each subject has a token bucket stored in a shared key-value cache. A missing bucket begins full. Refill lazily when a request arrives: add elapsed_time * refill_rate, capped at capacity. If time has not advanc…

Practice focusAccept only when the refilled balance covers the full request, then subtract it. A rejected request spends nothing. Persist the refilled state in either case. A backward-moving clock must not create tokens. TokenBucket and the in-memory DistributedCache test double are provided. This base task is sequential; the cache name does not imply atomic distributed behavior. Refill returns a new bucket without editing its argument. Existing buckets retain their stored capacity/refill rate; call configuration initializes missing buckets only.…

Public brief

Topic tags
Python
Data structures

xAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026

Weighted LRU Cache

Build an LRU cache whose capacity is the total weight of stored entries rather than the number of keys.

Practice focusget returns -1 when absent and marks a hit most-recently used. put inserts or replaces a key. On replacement, remove the old weight before checking capacity. Evict least-recently used entries until the new value fits; one insertion may evict several entries. A non-positive size or a size exceeding capacity raises ValueError without changing the cache. Exact fits are valid. Target average O(1) time for get and for each individual insert, update, or eviction. The provided run case owns fixture dispatch and is not candidate work.…

Public brief

Topic tags
Python
Algorithms
Data structures
Storage & state
Networking

Coding exerciseCodingAI-generated

Practice formatRunnable coding45 min

Reported interview periodN/A

Sliding-window rate limiter

Build a limiter, then add quota reporting, retry timing, and independent keys.

Practice focusPython, Queues, State, Boundary cases, Complexity through a runnable coding exercise.

Public brief

Topic tags
Python
Algorithms
Data structures
Product design
Communication

Coding exerciseCodingAI-generated

Practice formatRunnable coding45 min

Reported interview periodN/A

Interval calendar

Reason about half-open intervals through conflicts, room counts, merging, and free slots.

Practice focusPython, Sorting, Intervals, Heaps, Edge cases through a runnable coding exercise.

Public brief

Topic tags
Python
Data structures
Reliability
Data / SQL

Coding exerciseCodingAI-generated

Practice formatRunnable coding50 min

Reported interview periodN/A

Dependency-ready scheduler

Turn a dependency graph into stable ready sets, execution layers, and failure impact.

Practice focusPython, Graphs, Stable ordering, Cycle detection, Failure analysis through a runnable coding exercise.

Public brief

Topic tags
Python
Data structures
Storage & state

Coding exerciseCodingAI-generated

Practice formatRunnable coding50 min

Reported interview periodN/A

Streaming metric window

Compute ordered rolling metrics, then partition state and expose freshness explicitly.

Practice focusPython, Queues, Streaming state, Boundaries, Observability through a runnable coding exercise.

Public brief

Topic tags
Data structures
Reliability

System designSystem designAI-generated

Practice formatWritten response45 min

Reported interview periodN/A

Warm a cold cache without a thundering herd

After a deploy the cache is empty and every request misses. Design a warming path that keeps origin load bounded, then explain how readers stay correct when warming dies halfway.

Practice focusCaching, Backpressure, Failure recovery through a written response exercise.

Public brief

Topic tags
Data structures
ML / AI
Data / SQL

AnthropicSystem designAI-generated

Practice formatWritten response45–60 min

Reported interview periodN/A

Make every document decision traceable to evidence

High-volume document review needs extraction, model judgment, evidence links, and a human queue whose decisions can be defended later. Design the pipeline and the versioning that keep it auditable.

Practice focusPipeline design, Evidence linking, Human-in-the-loop review, Versioning through a written response exercise.

Public brief

Topic tags
Algorithms
Data structures
Storage & state
Reliability
Data / SQL

OpenAISystem designAI-generated

Practice formatWritten response45–60 min

Reported interview periodN/A

A mutable indexed sequence that must restart exactly

Design a sequence that stays fast to index, accepts mutation, and can crash at any point without losing the state a reader already saw. Then make the restart path provable rather than plausible.

Practice focusData structure design, Complexity analysis, Durability, Crash recovery through a written response exercise.

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Grade book

An in-memory grade book with a ranking that does not treat a missing score as zero.

Practice focusState, Ranking, Edge cases through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Practice formatWritten response40 minutes

Reported interview periodN/A

Launch order

Return one valid order of steps, or report a cycle.

Practice focusOrdering, Cycles through a written response exercise.

Previous2 of 2Next

Browse all original practice

Build a token-budget batcher
Sliding-window rate limiter
Interval calendar
Nested dictionary transforms
Command-log store
Dependency-ready scheduler
Streaming metric window
Evaluation slice aggregator
Build a reliable job runner
Build one adaptable decision story
Defend your role fit
Prepare one project deep dive
Design an evaluation artifact registry
Defend a reversible launch decision
Negotiate an ambiguous role scope
Trace a project from claim to evidence
Choose between two urgent priorities
Resolve a cross-functional disagreement
Own a consequential failure
Increase a team’s leverage
Warm a cold cache without a thundering herd
Ship a 500 GB checkpoint without a startup stampede
Make every document decision traceable to evidence
Share eight GPUs between two workloads with different promises
A mutable indexed sequence that must restart exactly
Trace a falling unit price to a rising bill
Keep a very long conversation usable while it streams
Design durable scheduled publishing
Make speculative code edits safe to accept
Recover a grouping rule from two-word phrases

CONTENT BOUNDARY

Independent frontier AI interview practice. Includes adaptations of collected interview material and original exercises; not official company questions and not affiliated with the companies represented. Collected material does not predict future interview questions. Report a correction.

Loading the question catalog…

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 46 Coding 36 System design 10 Behavioral 0 Hiring manager 0 Project deep dive 0

Topics

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

40 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Column order of a binary tree

Public brief

Topic tags
Python
Data structures
Reliability

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Jun 2026

Design a Type-Safe Durable LRU Cache

Extend a crash-recoverable LRU cache to support built-in containers and explicitly registered domain objects without using unsafe object serialization.

Public brief

Topic tags
Python
Data structures
Data / SQL

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–May 2026

Design a Weighted, Checkpointable Data Batcher

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

Return the k-th value in descending order from an integer array, treating equal values as separate entries. The input arrives in one of two line layouts.

New public brief

Topic tags
Python
Data structures
Communication

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Resumable Iterators

Implement an iterator over a copied list that can serialize its position and later resume at the next not-yet-yielded item. Then compose the same behavior across a sequence of lists.

New public brief

Topic tags
Python
Data structures
Storage & state
Networking

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Token-Bucket State Transitions

Public brief

Topic tags
Python
Data structures

xAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026

Weighted LRU Cache

Build an LRU cache whose capacity is the total weight of stored entries rather than the number of keys.

Public brief

Topic tags
Python
Algorithms
Data structures
Storage & state
Networking

Coding exerciseCodingAI-generated

Practice formatRunnable coding45 min

Reported interview periodN/A

Sliding-window rate limiter

Build a limiter, then add quota reporting, retry timing, and independent keys.

Practice focusPython, Queues, State, Boundary cases, Complexity through a runnable coding exercise.

Public brief

Topic tags
Python
Algorithms
Data structures
Product design
Communication

Coding exerciseCodingAI-generated

Practice formatRunnable coding45 min

Reported interview periodN/A

Interval calendar

Reason about half-open intervals through conflicts, room counts, merging, and free slots.

Practice focusPython, Sorting, Intervals, Heaps, Edge cases through a runnable coding exercise.

Public brief

Topic tags
Python
Data structures
Reliability
Data / SQL

Coding exerciseCodingAI-generated

Practice formatRunnable coding50 min

Reported interview periodN/A

Dependency-ready scheduler

Turn a dependency graph into stable ready sets, execution layers, and failure impact.

Practice focusPython, Graphs, Stable ordering, Cycle detection, Failure analysis through a runnable coding exercise.

Public brief

Topic tags
Python
Data structures
Storage & state

Coding exerciseCodingAI-generated

Practice formatRunnable coding50 min

Reported interview periodN/A

Streaming metric window

Compute ordered rolling metrics, then partition state and expose freshness explicitly.

Practice focusPython, Queues, Streaming state, Boundaries, Observability through a runnable coding exercise.

Public brief

Topic tags
Data structures
Reliability

System designSystem designAI-generated

Practice formatWritten response45 min

Reported interview periodN/A

Warm a cold cache without a thundering herd

After a deploy the cache is empty and every request misses. Design a warming path that keeps origin load bounded, then explain how readers stay correct when warming dies halfway.

Practice focusCaching, Backpressure, Failure recovery through a written response exercise.

Public brief

Topic tags
Data structures
ML / AI
Data / SQL

AnthropicSystem designAI-generated

Practice formatWritten response45–60 min

Reported interview periodN/A

Make every document decision traceable to evidence

High-volume document review needs extraction, model judgment, evidence links, and a human queue whose decisions can be defended later. Design the pipeline and the versioning that keep it auditable.

Practice focusPipeline design, Evidence linking, Human-in-the-loop review, Versioning through a written response exercise.

Public brief

Topic tags
Algorithms
Data structures
Storage & state
Reliability
Data / SQL

OpenAISystem designAI-generated

Practice formatWritten response45–60 min

Reported interview periodN/A

A mutable indexed sequence that must restart exactly

Design a sequence that stays fast to index, accepts mutation, and can crash at any point without losing the state a reader already saw. Then make the restart path provable rather than plausible.

Practice focusData structure design, Complexity analysis, Durability, Crash recovery through a written response exercise.

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Practice formatWritten response35 minutes

Reported interview periodN/A

Grade book

An in-memory grade book with a ranking that does not treat a missing score as zero.

Practice focusState, Ranking, Edge cases through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Practice formatWritten response40 minutes

Reported interview periodN/A

Launch order

Return one valid order of steps, or report a cycle.

Practice focusOrdering, Cycles through a written response exercise.

Previous2 of 2Next

Browse all original practice

Build a token-budget batcher
Sliding-window rate limiter
Interval calendar
Nested dictionary transforms
Command-log store
Dependency-ready scheduler
Streaming metric window
Evaluation slice aggregator
Build a reliable job runner
Build one adaptable decision story
Defend your role fit
Prepare one project deep dive
Design an evaluation artifact registry
Defend a reversible launch decision
Negotiate an ambiguous role scope
Trace a project from claim to evidence
Choose between two urgent priorities
Resolve a cross-functional disagreement
Own a consequential failure
Increase a team’s leverage
Warm a cold cache without a thundering herd
Ship a 500 GB checkpoint without a startup stampede
Make every document decision traceable to evidence
Share eight GPUs between two workloads with different promises
A mutable indexed sequence that must restart exactly
Trace a falling unit price to a rising bill
Keep a very long conversation usable while it streams
Design durable scheduled publishing
Make speculative code edits safe to accept
Recover a grouping rule from two-word phrases

CONTENT BOUNDARY