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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 162 Python 161 Algorithms 36 Data structures 36 Concurrency 19 Distributed systems 7 Storage & state 23 Networking 6 Reliability 9 ML / AI 12 Data / SQL 17 Security 4 Product design 9 Communication 5

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

155 questions

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

Coding results

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

New public brief

Topic tags
Python
Algorithms
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Choose the Best Transit Mode Through a Grid

A grid contains a start S, a destination D, blocked cells, and cells labeled by transit mode. A trip must use one mode for its entire route. Choose the reachable mode with the best travel time and cost.

Practice focusRequirements - Digit '1' identifies modes[0] , digit '2' identifies modes[1] , and so on. - Movement is allowed in four cardinal directions through cells of the chosen digit. - S and D may be entered for free and add neither time nor cost. - X , unrelated mode digits, and any other symbols are blocked. - For a route using mode i , each mode cell contributes times[i] and costs[i] . - Choose minimum total time, then minimum total cost, then earlier position in modes . Return "" if no mode reaches D .…

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.

Public brief

Topic tags
Python
Algorithms
Concurrency
Product design

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026–Aug 2026

Parallel Prefix Matrix Products with Autograd

Given square matrices W[0..n-1], compute inclusive prefix products P[i] = W[0] @ ... @ W[i] using a Hillis–Steele doubling scan, then implement the backward pass without relying on an automatic-differentiation …

Practice focusRequirements - weights has shape (n, d, d) ; return prefixes with the same shape. - Each scan round combines entries 2 r positions apart, using out-of-place round updates so values from one round are not mixed with the next. - Backward returns the gradient for every input matrix for an arbitrary gradient on every prefix. - Handle n=0 , n=1 , non-commutativity, and floating-point dtype consistently. - Explain saved intermediates and complexity in sequential work, parallel depth, and memory. Follow-ups 1.…

Public brief

Topic tags
Python
Data structures
Concurrency

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Mode-Compatible Lock with Fair Batching

Implement a lock that may be held concurrently by many threads only when they request the same mode. A different mode waits until all current holders release. Then add fairness across queued modes.

Practice focusRequirements - try acquire grants immediately or queues (tid, mode) without duplicates. - release releases one holder of that mode and returns newly granted thread IDs. - Base lock may admit a new same-mode requester while that mode is active. - Fair lock prevents barging once another mode is queued. - When the next queued mode becomes eligible, grant the contiguous batch already waiting for that mode. - Reject invalid releases and define per-thread ownership. Follow-ups 1. Implement blocking acquire with a condition variable. 2.…

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

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.…

Public brief

Topic tags
Python
Algorithms
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Aug 2026

Delete a Position from Interval Coverage

A compact coverage set is represented by sorted, non-overlapping, non-touching inclusive intervals. If the covered values were expanded into one ordered sequence, delete the value at a given zero-based position…

Practice focusFor example, [(4, 7), (10, 11), (13, 15)] represents 4,5,6,7,10,11,13,14,15 . Deleting position 2 removes value 6 , producing [[4, 5], [7, 7], [10, 11], [13, 15]] . Requirements - Return intervals as [start, end] pairs. - Preserve sorted, non-overlapping, non-touching output. - A deletion may shrink an endpoint, remove a singleton interval, or split an interval in two. - Assume index refers to an existing covered value; state how you would report an invalid index. - Do not expand every covered integer when ranges may be large.…

Public brief

Topic tags
Python
Concurrency
Reliability

DatabricksCoding

Talk-through codingNo local grader

Reported interview periodNov 2025–Aug 2026

Durable Multi-Threaded Log Writer

Implement a log writer that accepts binary records from multiple threads and durably appends each complete record to a file.

Practice focusRequirements - Encode each record as a four-byte big-endian length followed by its payload. - push returns only after all bytes for that record are written and the file is synchronized to durable storage. - A record's bytes must never interleave with another record. - Calls from one thread retain program order; calls from different threads may appear in either order. - close must coordinate with active or future pushes and be idempotent. - Handle partial writes, I/O errors, and payload lengths that cannot be represented.…

Public brief

Topic tags
Python
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Hybrid Run-Length and Bit-Packing Codec

Implement a reversible encoder for an integer sequence using run-length blocks for long runs and fixed-size literal blocks otherwise.

Practice focusRequirements and format - A run of at least eight equal values becomes ["RLE", value, count] and consumes the full run. - Otherwise consume the next eight values as ["BP", values] . - A final block may contain fewer than eight values. If every remaining value is equal, encode it as RLE; otherwise use a short BP block. - Walk strictly left to right, making output deterministic. decode must validate the entire block sequence before reconstructing it.…

New public brief

Topic tags
Python
Concurrency
ML / AI

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Build a Tool-Using Research Agent

You are given an LLM client whose responses may contain text blocks or one or more tool-call blocks. Build an agent that answers a user question by repeatedly calling the model, executing requested tools, retur…

Practice focusAssume two tools are available: a stock-price lookup and a shares-outstanding lookup. A question may require one lookup, several independent lookups, or combining results such as market capitalization. Requirements - Preserve the complete conversation history, including assistant tool calls and matching tool results. - Execute every tool call in a response; do not silently discard parallel calls. - Match each result to its tool-call identifier. - Stop only on a final model response, and return its text.…

New public brief

Topic tags
Python
Data structures
Storage & state

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodApr 2026–Aug 2026

Convert Sampled Call Stacks into Events

A profiler periodically records the active call stack. Convert these snapshots into the minimal sequence of call-start and call-end events.

Practice focusEach sample has an integer timestamp and a stack ordered from outermost to innermost. Each output event contains the sample timestamp, an event type ( start or end ), and a frame name. Rules - Compare each stack with the previous stack using the longest common prefix. - End removed frames from innermost to outermost. - Start added frames from outermost to innermost. - Adjacent identical stacks produce no events. - Equal names at different depths represent different invocations. - Do not invent end events for calls still active in the last sample.…

Public brief

Topic tags
Python
Networking
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Ordered IPv4 Firewall Rules

Implement an ordered firewall policy for IPv4 addresses.

Practice focusEach rule is [action, cidr] , where action is "ALLOW" or "DENY" . Evaluate rules from top to bottom; the first network containing the address determines the result. If no rule matches, deny access. A rule without a prefix length represents one address, equivalent to /32 . Requirements - Parse and validate dotted-decimal IPv4 addresses and CIDR prefix lengths. - Correctly handle /0 , /32 , network boundaries, and overlapping rules. - Preserve first-match semantics; a more specific later rule does not override an earlier match.…

Previous4 of 7Next

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.

155 questions

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

Coding results

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

New public brief

Topic tags
Python
Algorithms
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Choose the Best Transit Mode Through a Grid

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.

Public brief

Topic tags
Python
Algorithms
Concurrency
Product design

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026–Aug 2026

Parallel Prefix Matrix Products with Autograd

Public brief

Topic tags
Python
Data structures
Concurrency

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Aug 2026

Mode-Compatible Lock with Fair Batching

Implement a lock that may be held concurrently by many threads only when they request the same mode. A different mode waits until all current holders release. Then add fairness across queued modes.

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

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.

Public brief

Topic tags
Python
Algorithms
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Aug 2026

Delete a Position from Interval Coverage

Public brief

Topic tags
Python
Concurrency
Reliability

DatabricksCoding

Talk-through codingNo local grader

Reported interview periodNov 2025–Aug 2026

Durable Multi-Threaded Log Writer

Implement a log writer that accepts binary records from multiple threads and durably appends each complete record to a file.

Public brief

Topic tags
Python
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Hybrid Run-Length and Bit-Packing Codec

Implement a reversible encoder for an integer sequence using run-length blocks for long runs and fixed-size literal blocks otherwise.

New public brief

Topic tags
Python
Concurrency
ML / AI

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Build a Tool-Using Research Agent

New public brief

Topic tags
Python
Data structures
Storage & state

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodApr 2026–Aug 2026

Convert Sampled Call Stacks into Events

A profiler periodically records the active call stack. Convert these snapshots into the minimal sequence of call-start and call-end events.

Public brief

Topic tags
Python
Networking
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Ordered IPv4 Firewall Rules

Implement an ordered firewall policy for IPv4 addresses.

Previous4 of 7Next

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