Frontier AI Technical Interview Question Bank

Topic tags
Data structures

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.…

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

Runnable 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
Data structures
Reliability
Data / SQL

Coding exerciseCodingAI-generated

Runnable 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

Runnable 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
Concurrency
Storage & state
Reliability
ML / AI

System designSystem designAI-generated

Written response75–100 min

Reported interview periodN/A

Build a reliable job runner

Review staged prompts that begin with a small in-memory worker, then introduce retries, duplication, cancellation, and process restarts.

Practice focusState modeling, Idempotency, Retry policy, Failure recovery, Operational reasoning through a written response exercise.

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Written 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

Written 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.

Frontier AI technical interview question bank.

Frontier AI technical interview question bank.

Compressed prefix tree

Token-Bucket State Transitions

Weighted LRU Cache

Sliding-window rate limiter

Dependency-ready scheduler

Streaming metric window

Build a reliable job runner

Grade book

Launch order

Compressed prefix tree

Token-Bucket State Transitions

Weighted LRU Cache

Sliding-window rate limiter

Dependency-ready scheduler

Streaming metric window

Build a reliable job runner

Grade book

Launch order