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Question bank

Frontier AI technical interview question bank.

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

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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 269 Coding 162 System design 48 Behavioral 29 Hiring manager 16 Project deep dive 14

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.

242 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
ML / AI

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Debug a minimal transformer computation

A small NumPy model produces incorrect attention outputs and fails to learn. Implement corrected versions of four operations used by a decoder-style model. The model dimension is small and attention uses one he…

Practice focusScenario A small NumPy model produces incorrect attention outputs and fails to learn. Implement corrected versions of four operations used by a decoder-style model. The model dimension is small and attention uses one head, so focus on tensor semantics rather than framework APIs. Interface Requirements pos embed Return token representations with positional embeddings added elementwise. Shapes must match or broadcast unambiguously. attention - Compute scaled dot-product attention using a scale of 1 / sqrt(d k) .…

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

A file hierarchy contains directories and files. Some files are already encrypted. You may encrypt an individual file or issue one recursive encryption request for an entire directory. Choose operations with mi…

Practice focusRequirements and cost model - Encrypting one file costs t req + t file . - Encrypting a directory costs t req + N t file , where N is every file in its subtree, including already-encrypted files. - A subtree with no unencrypted files costs 0 . - At a directory, you may batch the whole subtree or solve its children independently. count files returns (encrypted count, unencrypted count) . The input is a finite tree of FileNode and DirectoryNode objects, with boolean encryption flags, no cycles or shared nodes, and non-negative integer costs.…

Public brief

Topic tags
Python
Data structures
Distributed systems

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Sep 2026

Aggregate Count and Topology over a Machine Tree

Machines form a rooted tree and may communicate only with their parent or children. Implement message handling so the root can count all machines and reconstruct a deterministic topology string.

Practice focusRequirements - A count request propagates to children; a leaf replies 1 ; an internal node replies with one plus all child counts. - A topology request produces id(child1,child2,...) ; a leaf is id[] . - Only the root publishes the final result. - Correlate replies with operation type and wait for every expected child exactly once. - Do not assume child replies arrive in order; sort by child ID for deterministic topology. - Avoid blocking the message handler and state behavior for duplicate requests.…

New public brief

Topic tags
Python
Algorithms

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Contagion in a Grid

A rectangular grid contains empty cells (0), fresh items (1), and contaminated items (2). At each minute, every fresh item sharing an edge with a contaminated item becomes contaminated. All changes within a min…

Practice focusImplement: Return the number of minutes required for every fresh item to become contaminated. Return 0 if there are no fresh items initially, and -1 if at least one fresh item is unreachable. Diagonal neighbors do not interact. Aim for O(rows columns) time and space. Staged follow-ups 1. Return the earliest arrival time for every reachable cell from multiple sources. 2. Introduce blocked cells and targets, returning the time when all targets are reached. 3. You may remove at most one shared blocker for the entire propagation.…

New public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Stamp a supplied route onto a grid

Mark the open floor cells named in a coordinate list and return the resulting grid, leaving walls, the start, and the exit exactly as they were.

Practice focusRequirements - Line 1 is rows cols . The next rows lines are the grid, each exactly cols characters long. - A count follows the grid, then that many lines of row col . - Coordinates are zero-based and name the row first, then the column. - Replace a . at a listed coordinate with . If the cell holds S , E , , or is already , leave it unchanged. - Listing the same coordinate again has no additional effect. - Return the whole grid with each row on its own line, rows separated by a newline, and no extra text. - Every coordinate is inside the grid.…

New public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Shortest route through directional cells

Compute the fewest orthogonal moves from the start to the exit of a grid containing cells that can only be entered while travelling in one particular direction.

Practice focusRequirements - Line 1 gives rows cols . The next rows lines each contain exactly cols characters. - is a wall, S is the start, and E is the exit. - can be entered only by moving right into it. < can be entered only by moving left into it. - The restriction applies when entering a directional cell. Once inside, the walker may leave in any direction. - S , E , and ordinary open cells accept entry from any side. - Each move goes one cell up, down, left, or right and costs one step.…

New public brief

Topic tags
Python

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Compute File-System Size

A file-system node is either a file with a non-negative byte size or a directory containing child nodes. Hard links are possible, so the same node object may be reachable by more than one path and cycles may ex…

Practice focusImplement: Return the sum of the sizes of all distinct reachable files. Count a node at most once even if multiple paths reference it. An empty directory has size 0 . You may identify nodes by stable object identity. Aim for O(V + E) time and O(V) auxiliary space, where V is the number of distinct reachable nodes and E is the number of child references. Staged follow-ups 1. Provide an iterative traversal for inputs too deep for recursion. 2. Add memoization for repeated directory-size queries. 3.…

New public brief

Topic tags
Python
Algorithms

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Islands in a Dynamic Grid

You are given a rectangular binary grid. 1 represents land and 0 represents water. Cells belong to the same island when they share an edge; diagonal contact does not connect islands.

Practice focusFirst implement: Then support a grid that begins as all water. After each (row, column) operation, turn that cell into land and report the current island count: Adding an already-land cell leaves the count unchanged. Assume coordinates are in bounds. Staged follow-ups 1. Compare DFS, BFS, and disjoint-set solutions for the static problem. 2. Achieve near-constant amortized work per addition with union by rank and path compression. 3. Discuss the harder case in which land can also be removed.

New public brief

Topic tags
Python
Distributed systems
Storage & state
Reliability

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Circuit Breaker and Replica Failover

Implement a circuit breaker that protects a dependency after repeated failures, then use it to route work across database replicas.

Practice focusRequirements - CLOSED permits calls. A success resets the consecutive-failure count. - After failure threshold consecutive supplier failures, transition to OPEN and propagate the failure. - While OPEN , reject calls without invoking the supplier. - Raise the provided CircuitOpenError for breaker-generated denial; propagate supplier errors unchanged. An error message containing the word OPEN is not a denial signal. - After recovery timeout , permit one HALF OPEN probe. Success closes the breaker; failure reopens it and restarts the timeout.…

New public brief

Topic tags
Python
Algorithms
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Sum the in-range values of a search tree

Add up every node value that falls inside a closed interval in a binary search tree supplied as a level-order sequence.

Practice focusRequirements - Line 1 lists the tree in level order, comma separated, with null marking a missing child. - Line 2 holds low,high , both endpoints included. - Return the sum of all node values v with low <= v <= high as a decimal string. - Return "0" when the first token is null or when no value lies in the range. - The listing describes a valid binary search tree. - run case(case: dict) forwards case["stdin"] to solve . - Do not append a trailing newline to the returned string; return the value exactly once.

Public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Palindrome after one deletion

Decide whether a lowercase string becomes a palindrome when at most one character is removed.

Practice focusRequirements - The input is a single line holding the string; a trailing newline is formatting, not part of the value. - Removing nothing is allowed, so a string that already reads the same in both directions returns true . - On the first mismatched pair, exactly one of the two candidate removals can help; check both remainders. - Return true or false in lowercase, with no other text. - A one-character string qualifies, and so does an empty one. - Removing more than one character is a different task and is out of scope.

New public brief

Topic tags
Python

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Optimize a Numerical Kernel Under a Fixed Benchmark

You are given a correct but slow numerical kernel, representative inputs, a correctness checker, and a benchmark. Improve its measured throughput without changing its output contract.

Practice focusAssumption: the precise production kernel and hardware contract are unavailable in this preparation version. Begin by implementing and optimizing compatible rectangular matrix multiplication over numeric arrays: Reject incompatible or ragged inputs. Preserve numerical correctness within the stated tolerance and do not special-case benchmark inputs. For this preparation interface, matrices are nonempty rectangular lists with nonempty rows and finite real entries (booleans are not numbers).…

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
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Ancestor lookup with upward-only links

Every node in a tree stores only the id of its parent. Given two node ids, find their deepest shared ancestor using those upward links alone.

Practice focusRequirements - Line one is the node count n . Line two gives n parent ids in node order: the value at position i is the parent of node i , and a root is marked -1 . - Line three holds the two query ids separated by whitespace. - Node identity is the array position, so ids run from 0 to n - 1 . - A node counts as an ancestor of itself, so querying a node against one of its descendants returns that node. - Return the id of the deepest common ancestor as a decimal string, or -1 when the two nodes belong to different trees.…

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Shared ancestor of two nodes in a binary tree

A binary tree arrives in level-order form along with two node values. Identify the lowest node whose subtree contains both values.

Practice focusRequirements - Line one is the level-order values separated by commas; null marks a missing child and the line may be wrapped in [...] . - Line two holds the two target values separated by a comma. - Node values are unique, and both targets appear in the tree. - A node counts as its own descendant, so a parent and child query answers the parent. - Return the value of the lowest shared ancestor as a decimal string, not its position in the serialization. - When one candidate ancestor lies below another, report the deeper one.…

New public brief

Topic tags
Python
Data structures

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodAug 2026

Independent Lazy Iterators

Implement a utility that turns one input iterable into n iterators. Every returned iterator must yield the full source sequence in order, and consumers may advance at different speeds. Read each source value on…

Practice focusRaise ValueError when n < 1 . Source exceptions and exhaustion should propagate consistently to every consumer. Concurrent calls are out of scope for the initial implementation. Start with a correct design, then improve its memory usage so that buffered values are shared rather than copied into n independent queues. Space should be proportional to the distance between the fastest and slowest consumers plus per-consumer cursor state. Staged follow-ups 1. Explain when buffered values can safely be discarded. 2.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Pick the longest letter-disjoint word group

Given a list of lowercase words, choose a group in which no letter repeats, either inside a single word or across words, and report the largest total number of letters such a group can contain.

Practice focusRequirements - Line 1 holds the number of words. Line 2 holds exactly that many space-separated lowercase words. - A word may join the group only if all of its own letters are different. - No letter may be shared by two chosen words, so each of the 26 letters appears at most once in the whole group. - Words may be skipped, and selecting no words is allowed. - Maximize the total character count across the chosen words. - Return that maximum as a decimal string, using "0" when no word qualifies.…

Public brief

Topic tags
Python
Algorithms
Data / SQL

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Anagrammed Substring Search

Given a text and a query, find the first position at which a substring of the text is an anagram of the query. Two strings are anagrams when they contain the same characters with the same multiplicities, regard…

Practice focusRequirements Implement: Return the zero-based start index of the first matching window, or -1 when no match exists. An empty query matches at index 0 ; a query longer than the text has no match. Characters are initially compared exactly, including case. Aim for O(n + m) time for a text of length n and query of length m , rather than sorting every window. Additional assessed interfaces 1. Return every matching start index. For an empty query, return every boundary from 0 through len(lookup string) . 2.…

Public brief

Topic tags
Python
Storage & state
Reliability

OpenAICoding

Python codingWebAssembly + public tests2 versions

Reported interview periodNov 2025–Aug 2026

Persist a string map across restart

Implement a durable string-to-string key-value store using the provided FileSystem abstraction.

Practice focusIn the base task, shutdown() commits a complete snapshot using FileSystem.save blob(bytes) . A newly constructed store starts empty; restore() recovers the latest saved snapshot. The supplied storage replaces a whole blob atomically and remains alive across store instances. It models snapshot persistence, not partial writes or a real disk. Keys and values may contain arbitrary Unicode characters, including newlines; use a length-prefixed binary format rather than delimiter-only encoding. Do not use JSON or pickle.…

Public brief

Topic tags
Python
Storage & state

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Turn-Based Creature Battle

Implement a deterministic battle between two teams of creatures. Team A acts first. On each turn, the first living creature on the active team attacks the first living creature on the opposing team.

Practice focusRequirements - Damage reduces health; a creature with health <= 0 is knocked out and cannot act. - Alternate teams after every attack, skipping a side only if it has no living creature—at which point the battle ends. - Log every attack, knockout, and final winner in a deterministic format agreed before coding. - Do not mutate caller-owned teams unless the API explicitly documents it. - Validate empty teams, non-positive attack values, and battles that cannot make progress. Follow-ups 1. Order turns by speed rather than alternating teams. 2.…

New public brief

Topic tags
Python
Data structures

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJul 2025–Aug 2026

Reconstruct Stack Transitions from Samples and Events

Build utilities for converting between stack observations and call events. Stack frames are ordered outermost to innermost.

Practice focusFor an event stream, push on enter / start , pop on exit / end , record the stack after each event, and run-length encode adjacent identical stacks. For sampled stacks, compare adjacent samples using their longest common prefix. Emit removed frames as end events from innermost outward, then emit added frames as start events from outermost inward. Use the new sample's timestamp and leave frames in the final sample open. Samples have ts and stack fields; events emitted from samples have name , kind ( start or end ) and ts .…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Leftmost local maximum in a numeric sequence

Given a sequence whose adjacent values never tie, locate the first element that rises above every neighbor it has. Report that element's position.

Practice focusRequirements - The input is one line of space-separated integers with no count prefix, and it holds at least one value. - A position is a local maximum when its value is strictly greater than each neighbor that exists; the first and last positions have only one neighbor. - Return the zero-based index of the earliest such position as a decimal string. - A single-element sequence qualifies at index 0 . - Because neighbors never tie, at least one local maximum always exists and no equality rule is needed.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Count contiguous runs with a target sum

Given an integer array and a target, count the non-empty contiguous runs whose values add up to that target. Values may be zero or negative, so a qualifying run can begin and end anywhere.

Practice focusRequirements - The first line holds the element count and the target, separated by a space; the second line holds the values. - A variant layout puts only the count on the first line, the values on the second, and the target on the third; read the target from whichever position it occupies. - Count every start and end pair, including single elements and runs whose values are all zero. - The empty run never counts, and overlapping runs are counted separately. - Return the count as a decimal string with no other text.…

Public brief

Topic tags
Python
Data structures
Storage & state
Networking

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Follow graph with snapshots

Implement a directed social graph with add_user, follow, and create_snapshot.

Practice focusA snapshot must preserve the follow relationships that existed when it was created. Later mutations to the live graph must not change earlier snapshots. A snapshot supports is following , get following , get followers , and recommend . Self-follows and repeated follows are no-ops. Rank recommendations by the number of two-hop mutual connections in descending order, then by user id in ascending order; return at most k users. Exclude the requesting user and accounts they already follow. Follow-ups 1. Add unfollow while preserving earlier snapshots. 2.…

Previous6 of 11Next

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 269 Coding 162 System design 48 Behavioral 29 Hiring manager 16 Project deep dive 14

Topics

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

242 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
ML / AI

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Debug a minimal transformer computation

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

Public brief

Topic tags
Python
Data structures
Distributed systems

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Sep 2026

Aggregate Count and Topology over a Machine Tree

Machines form a rooted tree and may communicate only with their parent or children. Implement message handling so the root can count all machines and reconstruct a deterministic topology string.

New public brief

Topic tags
Python
Algorithms

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Contagion in a Grid

New public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Stamp a supplied route onto a grid

Mark the open floor cells named in a coordinate list and return the resulting grid, leaving walls, the start, and the exit exactly as they were.

New public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Shortest route through directional cells

Compute the fewest orthogonal moves from the start to the exit of a grid containing cells that can only be entered while travelling in one particular direction.

New public brief

Topic tags
Python

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Compute File-System Size

New public brief

Topic tags
Python
Algorithms

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Islands in a Dynamic Grid

You are given a rectangular binary grid. 1 represents land and 0 represents water. Cells belong to the same island when they share an edge; diagonal contact does not connect islands.

New public brief

Topic tags
Python
Distributed systems
Storage & state
Reliability

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Circuit Breaker and Replica Failover

Implement a circuit breaker that protects a dependency after repeated failures, then use it to route work across database replicas.

New public brief

Topic tags
Python
Algorithms
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Sum the in-range values of a search tree

Add up every node value that falls inside a closed interval in a binary search tree supplied as a level-order sequence.

Public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Palindrome after one deletion

Decide whether a lowercase string becomes a palindrome when at most one character is removed.

New public brief

Topic tags
Python

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Optimize a Numerical Kernel Under a Fixed Benchmark

You are given a correct but slow numerical kernel, representative inputs, a correctness checker, and a benchmark. Improve its measured throughput without changing its output contract.

Public brief

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodApr 2026–Aug 2026

Design Photo Sharing with Content Deduplication

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Ancestor lookup with upward-only links

Every node in a tree stores only the id of its parent. Given two node ids, find their deepest shared ancestor using those upward links alone.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Shared ancestor of two nodes in a binary tree

A binary tree arrives in level-order form along with two node values. Identify the lowest node whose subtree contains both values.

New public brief

Topic tags
Python
Data structures

GoogleCoding

Python codingWebAssembly + public tests

Reported interview periodAug 2026

Independent Lazy Iterators

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Pick the longest letter-disjoint word group

Given a list of lowercase words, choose a group in which no letter repeats, either inside a single word or across words, and report the largest total number of letters such a group can contain.

Public brief

Topic tags
Python
Algorithms
Data / SQL

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Anagrammed Substring Search

Public brief

Topic tags
Python
Storage & state
Reliability

OpenAICoding

Python codingWebAssembly + public tests2 versions

Reported interview periodNov 2025–Aug 2026

Persist a string map across restart

Implement a durable string-to-string key-value store using the provided FileSystem abstraction.

Public brief

Topic tags
Python
Storage & state

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Aug 2026

Turn-Based Creature Battle

Implement a deterministic battle between two teams of creatures. Team A acts first. On each turn, the first living creature on the active team attacks the first living creature on the opposing team.

New public brief

Topic tags
Python
Data structures

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJul 2025–Aug 2026

Reconstruct Stack Transitions from Samples and Events

Build utilities for converting between stack observations and call events. Stack frames are ordered outermost to innermost.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Leftmost local maximum in a numeric sequence

Given a sequence whose adjacent values never tie, locate the first element that rises above every neighbor it has. Report that element's position.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Count contiguous runs with a target sum

Given an integer array and a target, count the non-empty contiguous runs whose values add up to that target. Values may be zero or negative, so a qualifying run can begin and end anywhere.

Public brief

Topic tags
Python
Data structures
Storage & state
Networking

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Aug 2026

Follow graph with snapshots

Implement a directed social graph with add_user, follow, and create_snapshot.

Previous6 of 11Next

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