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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.

139 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.

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
Concurrency
Distributed systems
Data / SQL

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Aug 2026

Compute Mode and Median Across Distributed Shards

The same function runs on N workers. Each worker can read only its local shard of signed integers and communicate using send, recv, and barrier. Worker 0 returns the final answer; other workers return None.

Practice focusRequired results - Mode: the globally most frequent value; break ties by choosing the smaller value. - Median: the middle value for odd cardinality and the mean of the two middle values for even cardinality. - Every worker must participate in a protocol that terminates without unmatched receives or barriers. - Avoid sending complete shards when a smaller exact representation is available. Assume at least one value globally, though individual shards may be empty. Values are signed 64-bit integers.…

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.…

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
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.…

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.…

Public brief

Topic tags
Python
ML / AI
Product design

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Implement Batched Scaled Dot-Product Attention

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

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

Public brief

Topic tags
Python
Data structures
Concurrency

OpenAICoding

Python codingWebAssembly + public tests2 versions

Reported interview periodDec 2025–Aug 2026

First-fit heap blocks

Implement a memory allocator over a fixed contiguous address range. Maintain free blocks in a doubly linked list ordered by starting address.

Practice focusallocate(size) must select the first block large enough for the request. Remove an exact-fit block; otherwise advance its start address and reduce its size. Return the allocated start address, or -1 when no block can satisfy the request. free(address, size) returns a region to the free list. Insert it in address order and coalesce it with an adjacent block on the left, right, or both sides when their boundaries touch. Preserve list ordering and links after every operation. Follow-ups 1. Reject overlapping or double frees without corrupting state. 2.…

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Aug 2026

Build and Scale an Image-Transformation Pipeline

Given a directory of source images and a directory of transformation specifications, produce one output for every image/specification pair. Each specification contains an ordered sequence selected from grayscal…

Practice focusUse the provided naming callback for every result. Apply transformations in order and save valid output images. Scaling truncates the computed dimensions to integers; rotation expands the canvas. Requirements and edge cases - Discover supported image and specification files recursively or according to the supplied listing helper. - Do not share mutable image objects across independent pipelines. - Ensure all scheduled work completes before returning and propagate worker failures.…

Public brief

Topic tags
Python
Data structures

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodSep 2025–Aug 2026

Find Duplicate Files Efficiently

Walk a directory tree and return groups of files whose complete byte contents are identical.

Practice focusEach returned path must be absolute and resolved. Omit groups containing only one file. Group and path order are not significant. Requirements - Skip symbolic links and continue past files that become unreadable. - Treat multiple empty files as duplicates. - Avoid reading every byte of every file when cheap evidence can rule out equality. - A full-content comparison or collision-resistant digest must confirm every reported group. - Stream large files in bounded-size blocks rather than loading them entirely into memory.…

Public brief

Topic tags
Python
Data / SQL

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Aug 2026

Online softmax entropy

Implement numerically stable softmax, log-softmax, and entropy for a vector of logits. The standard entropy is -Σ p log p.

Practice focusThen implement a block-wise variant that processes the logits in bounded-size chunks without losing numerical stability. The block-wise result must match the full-vector computation within floating-point tolerance. Handle very large and very small logits, empty inputs according to the provided contract, and both supported entropy-sign conventions. Explain why subtracting the maximum logit prevents overflow and how partial statistics combine across blocks. Follow-ups 1. Return gradients with respect to the logits. 2.…

Public brief

Topic tags
Python
Algorithms
Concurrency
Distributed systems
ML / AI

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodJul 2026–Aug 2026

Debug sharded matrix-multiplication gradients

Implement forward and backward matrix multiplication across world workers.

Practice focusSplit A evenly by rows, replicate B , compute each local A i @ B , and concatenate the local outputs in row order. For the backward pass, compute each local dA i = dY i @ B.T , concatenate the dA i blocks, and compute the global dB as the sum of A i.T @ dY i across workers. Return results that match an unsharded NumPy implementation. Validate matrix shapes and explain the communication required by the forward and backward passes. Follow-ups 1. Shard B instead and compare communication costs. 2. Add uneven row partitions and preserve output ordering. 3.…

Previous4 of 6Next

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.

139 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.

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
Concurrency
Distributed systems
Data / SQL

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Aug 2026

Compute Mode and Median Across Distributed Shards

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

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
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

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.

Public brief

Topic tags
Python
ML / AI
Product design

AnthropicCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Aug 2026

Implement Batched Scaled Dot-Product Attention

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

Public brief

Topic tags
Python
Data structures
Concurrency

OpenAICoding

Python codingWebAssembly + public tests2 versions

Reported interview periodDec 2025–Aug 2026

First-fit heap blocks

Implement a memory allocator over a fixed contiguous address range. Maintain free blocks in a doubly linked list ordered by starting address.

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Aug 2026

Build and Scale an Image-Transformation Pipeline

Public brief

Topic tags
Python
Data structures

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodSep 2025–Aug 2026

Find Duplicate Files Efficiently

Walk a directory tree and return groups of files whose complete byte contents are identical.

Public brief

Topic tags
Python
Data / SQL

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Aug 2026

Online softmax entropy

Implement numerically stable softmax, log-softmax, and entropy for a vector of logits. The standard entropy is -Σ p log p.

Public brief

Topic tags
Python
Algorithms
Concurrency
Distributed systems
ML / AI

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodJul 2026–Aug 2026

Debug sharded matrix-multiplication gradients

Implement forward and backward matrix multiplication across world workers.

Previous4 of 6Next

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