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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.

216 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
Storage & state

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Jul 2026

Build a Temporal In-Memory Database with Backup and Restore

Process timestamped commands over records that map string keys to string field/value pairs. Timestamps are unique and strictly increasing; each command returns one string.

Practice focusCommand contract Every command is a list of strings. t , ttl and target are decimal integer strings. Command timestamps t are nonnegative and strictly increasing across the entire input; ttl is positive. Keys and field names are nonempty strings. Values may be empty strings. Inputs contain only the commands below with the stated argument counts. Return one output string for each input command, in order. | Command | Output | | --- | --- | | ["SET", t, key, field, value] | "" ; replace the field with a permanent value.…

Public brief

Topic tags
Python

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodJun 2026–Jul 2026

Repair a Looping Instruction Program

A small virtual machine executes a list of instructions over one integer accumulator. Blank lines and comment lines are ignored.

Practice focus- plus n : add n to the accumulator and move to the next instruction. - next n : ignore n and move to the next instruction. - jump n : move to the instruction at current index + n . Execution halts when the program counter moves outside the instruction list. It loops when it is about to execute an instruction that has already run. Exactly one jump or next instruction was swapped while keeping its operand. Interface Return -1 from the first two functions if the original program already halts.…

Public brief

Topic tags
Python
Product design

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Infer return types in a tiny generic type system

Implement type substitution for a small language. Types are either atomic names, such as int or generic T, or product types containing an ordered list of child types. A function describes parameter templates an…

Practice focusScenario Implement type substitution for a small language. Types are either atomic names, such as int or generic T , or product types containing an ordered list of child types. A function describes parameter templates and an output-type template. Given concrete argument types, infer the concrete return type. Treat int , float , str , bool , and char as concrete primitives. Any other atomic name in a function template is a generic variable.…

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2025–Jul 2026

Build a Bank Ledger with Held Transfers and Account Merges

Implement an in-memory banking service whose operations arrive in nondecreasing timestamp order.

Practice focusRequirements - Account creation starts at zero and returns True , or False if that identifier is already active. Deposits and withdrawals return the total balance, including held funds; invalid accounts or invalid amounts return None . A zero deposit is a read of the current balance. Negative deposits, and zero or negative withdrawals and transfers, are invalid. - Starting a transfer requires both accounts to exist and available funds (total balance minus holds) to cover the amount.…

Public brief

Topic tags
Python
ML / AI

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Jun 2026

Implement a Longest-Match Tokenizer

Given an input string and a vocabulary, tokenize from left to right using longest-prefix matching.

Practice focusAt each position, emit the integer ID of the longest vocabulary entry matching the remaining text. If nothing matches, emit vocab["UNK"] and advance by one character. With collapse unk=True , collapse consecutive unknown IDs into a single ID; otherwise emit one for each unmatched character. The literal vocabulary entry UNK is reserved and must not match input text as an ordinary token. Assume every token has a distinct integer ID and the vocabulary contains UNK . Requirements and edge cases - Return an empty list for empty input.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJun 2026

Shortest distinguishing prefix per word

Given a list of distinct lowercase words, return for each word the shortest opening slice that no other word in the list also starts with, preserving input order.

Practice focusRequirements - The first input line is the word count n ; the next n lines each hold one lowercase word. - Emit one prefix per line in input order, joined by newlines, with no summary line and no trailing separator. - Each prefix must be a leading slice of its own word and must not be a leading slice of any other word in the list. - Prefer the shortest qualifying slice: extend the prefix only until the character that no other word shares at that depth. - A list holding a single word uses that word's first character.…

Public brief

Topic tags
Python
Communication

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Jun 2026

Implement a Versioned Recipe Manager

Build an in-memory recipe service with unique names, search, users, and rollback.

Practice focusRecipe IDs and names are unique; name comparison and search are case-insensitive while original casing is preserved. Returned recipes must be defensive copies. Search results sort by ingredient count and then recipe ID. Successful adds and edits append immutable, one-based versions. IDs and names are nonempty strings; ingredients are lists of strings, preserving order and repetitions. Name uniqueness and substring search compare Python-style lowercase strings, without trimming or accent normalization. An empty search query matches every recipe.…

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Jun 2026

Implement a Same-Host Web Crawler

You are given a seed URL and a parser object. Calling htmlParser.getUrls(url) returns the links found on that page. Return every reachable URL whose hostname matches the seed URL's hostname, including the seed …

Practice focusRequirements - Visit each accepted URL at most once. - Never follow a link to another hostname. - Use the supplied parser rather than implementing HTTP fetching. - Return all reachable accepted URLs; result order is not significant. - Treat complete URL strings as visit identities. Compare parsed hostnames, not hostname substrings; different ports and schemes on the same hostname remain eligible. Assume syntactically valid absolute HTTP(S) URLs. No URL canonicalization, redirect fetching or network access is required.…

Public brief

Topic tags
Python
Data structures
Reliability

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Jun 2026

Design a Type-Safe Durable LRU Cache

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

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

Public brief

Topic tags
Python
Storage & state

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJul 2025–May 2026

Implement a Quota-Aware Cloud File Store

Process a sequence of string commands against a flat cloud-storage namespace. Every command returns one result string.

Practice focusOperations - Add a file with a unique name and integer size; copy an existing file to a free name; query a file's size. - Find files matching both a prefix and suffix, sorted by size descending and then name ascending. - Add quota-limited users and add user-owned files only when capacity permits. - Reduce a user's capacity, evicting that user's largest files first and using name order to break ties until usage fits. - Compress an owned file by renaming it with a .COMPRESSED suffix and halving its even size.…

Public brief

Topic tags
Python
Storage & state
Networking

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodMay 2026

Implement a DNS Resolver with Aliases and TTL

Build an in-memory resolver over A and CNAME records.

Practice focusRequirements - Normalize domain names case-insensitively and ignore a trailing dot. - An A record resolves directly to its address while live. - A CNAME follows its target recursively until a live A record is found. - Each record has type ( A or CNAME ) and value (address or target). Optional ttl is a duration; set at defaults to zero. A missing or null ttl means no expiration. - A record expires when now = set at + ttl . - Any expired or missing link makes resolution fail.…

Public brief

Topic tags
Python
Storage & state
Communication

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodMay 2026

Implement a Task Manager with Expiration and Historical Views

Tasks are scoped by (user, task_id). Implement creation, mutation, TTL expiration, and snapshots.

Practice focusRequirements - A task key can be created only once, even if the task later completes or expires. - Only live incomplete tasks can be updated or completed. - TTL is anchored at creation; a task is absent at and after created at + ttl , and updates do not refresh it. - Current lists contain live incomplete titles ordered by task ID. - A historical list includes all events at or before the requested timestamp and applies expiration relative to that historical time. - Calls arrive in nondecreasing command time, though historical query times may be earlier.…

Public brief

Topic tags
Python
Data structures
Data / SQL

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–May 2026

Design a Weighted, Checkpointable Data Batcher

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

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

Public brief

Topic tags
Python
Concurrency
ML / AI

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–May 2026

Build a Workforce Time and Pay System

Implement employee time tracking, ranking, deferred promotions, and bonus-pay windows. Time is measured in integer ticks.

Practice focusRequirements - Each independent call sequence begins with a new Workforce. Add employees with sequential IDs e1 , e2 , and so on, even when names repeat. Mutation methods return None ; IDs are determined by insertion order rather than returned by add employee. - Inputs use integer, nonnegative timestamps and rates, with rate interpreted as pay per time tick. k is nonnegative; return at most k workers, including zero-work employees. Employee IDs are compared lexicographically for ties. - Count only completed half-open clock sessions [in, out) .…

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

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

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

Public brief

Topic tags
Python
Concurrency
Distributed systems
Storage & state
Data / SQL

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–May 2026

Design Worker and Coordinator Protocols for Distributed Statistics

You control N workers and one coordinator. Worker i can read only shard i. Endpoints communicate by messages; there is no shared mutable dataset. Sending captures an independent snapshot of the payload; later s…

Practice focusThe task is either mode or median . For mode, return the globally most frequent integer with the smaller value winning ties. For median, return the exact middle value as a float, or the mean of the two middle values for even cardinality. The global input is non-empty; individual shards may be empty. Requirements - Define message shapes and an explicit completion condition. - Do not assume the coordinator can read worker data directly. - Avoid shipping complete raw shards in the scalable solution.…

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Fewest inserts to balance brackets

Report how many bracket characters must be inserted anywhere in a parenthesis string to make every prefix and the whole line balanced.

Practice focusRequirements - The input is one line containing only ( and ) . - A string is balanced when every prefix has at least as many ( as ) , and the total counts are equal. - Insertions may be placed at any position. Removing, replacing, or reordering characters is not allowed. - Return the minimum number of inserted characters as a decimal string. - A line that is already balanced returns "0" . - 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 periodApr 2026

Tightest slice covering a character multiset

Find the shortest contiguous slice of a source string that contains every character of a required multiset with at least the required multiplicity, and return that slice.

Practice focusRequirements - Line 1 is the source string. Line 2 lists the required characters. - The chosen slice must be contiguous and must contain each required character at least as many times as it appears on line 2. - Compare slices by length. When several slices tie for the shortest length, return the one that begins earliest. - If no slice qualifies, return an empty string. - Matching is case-sensitive. - Return the slice itself, not its length and not its bounds. - run case(case: dict) forwards case["stdin"] to solve .…

Public brief

Topic tags
Python
ML / AI

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Apr 2026

Debug a GRPO Training Step

A small PyTorch implementation of Group Relative Policy Optimization runs without exceptions but learns poorly. Inspect and correct its sampling, advantage normalization, and clipped policy loss while preservin…

Practice focusRequired behavior - Convert logits to probabilities with softmax before sampling tokens. - For each prompt group, compute A i = (r i - mean(r)) / (std(r) + eps) using a positive epsilon so zero-variance groups remain finite. - Compute the per-token importance ratio as exp(current logprob - old logprob) . - Exclude masked tokens from both the loss sum and averaging denominator. - Compute the negative mean of the minimum between the unclipped and clipped ratio times advantage. - Return a finite zero loss if every token is masked.…

New public brief

Topic tags
Python
Concurrency

xAICoding

Talk-through codingNo local grader

Reported interview periodNov 2025–Apr 2026

Make a Bank Account Thread-Safe

You are given a BankAccount whose deposit method performs a read-modify-write operation and may pause between reading and writing. You cannot modify that class. Implement a subclass that makes deposits safe whe…

Practice focusCall the inherited implementation rather than copying it. Two deposits of 500 and 700 into an account starting at 0 must finish with 1200 . Ensure the lock is released if the inherited method raises. The supplied constructor creates the account and its lock. Complete deposit only. The provided run case adapter owns the concurrent fixture execution; it is not candidate work. Opening balances and deposit amounts are integers, and deposit amounts are nonnegative. Empty deposit lists leave the opening balance unchanged. Each successful call returns None .…

New public brief

Topic tags
Python
Data structures
Communication

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Resumable Iterators

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

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

New public brief

Topic tags
Python
Storage & state

xAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Apr 2026

In-Memory Database with Expiry and Snapshots

Build an in-memory database in four stages. Each key owns string field/value pairs.

Practice focusMissing values return "" . Scans emit field(value) entries sorted by field. A TTL value is live over [created at, created at + ttl) . A backup captures all live fields and each field's remaining lifetime. Restore selects the newest backup at or before timestamp to restore , replaces current state, and restarts remaining lifetimes at timestamp . Assume timestamps supplied to mutating timed operations are nondecreasing. Backups must not share mutable state with the live database.…

New public brief

Topic tags
Python
Data structures
Storage & state
Networking

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Token-Bucket State Transitions

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

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

New public brief

Topic tags
Python

xAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026

Flatten and Rebuild Nested Values

A nested value contains integer leaves and internal list, tuple, or dict nodes. Dictionaries are traversed in insertion order.

Practice focusImplement: flatten returns leaves in traversal order. unflatten uses structure as a shape template and rebuilds the same container types while replacing leaves from left to right. Raise ValueError when there are too few or too many replacement values, and TypeError for unsupported nodes, including booleans. Empty containers must round-trip. Replacement values must be a list of non-boolean integers; reject other values with TypeError . Do not modify either input.…

Previous7 of 9Next

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.

216 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
Storage & state

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Jul 2026

Build a Temporal In-Memory Database with Backup and Restore

Process timestamped commands over records that map string keys to string field/value pairs. Timestamps are unique and strictly increasing; each command returns one string.

Public brief

Topic tags
Python

AnthropicCoding

Talk-through codingNo local grader

Reported interview periodJun 2026–Jul 2026

Repair a Looping Instruction Program

A small virtual machine executes a list of instructions over one integer accumulator. Blank lines and comment lines are ignored.

Public brief

Topic tags
Python
Product design

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Infer return types in a tiny generic type system

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2025–Jul 2026

Build a Bank Ledger with Held Transfers and Account Merges

Implement an in-memory banking service whose operations arrive in nondecreasing timestamp order.

Public brief

Topic tags
Python
ML / AI

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Jun 2026

Implement a Longest-Match Tokenizer

Given an input string and a vocabulary, tokenize from left to right using longest-prefix matching.

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodJun 2026

Shortest distinguishing prefix per word

Given a list of distinct lowercase words, return for each word the shortest opening slice that no other word in the list also starts with, preserving input order.

Public brief

Topic tags
Python
Communication

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Jun 2026

Implement a Versioned Recipe Manager

Build an in-memory recipe service with unique names, search, users, and rollback.

Public brief

Topic tags
Python

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodSep 2025–Jun 2026

Implement a Same-Host Web Crawler

Public brief

Topic tags
Python
Data structures
Reliability

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Jun 2026

Design a Type-Safe Durable LRU Cache

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

Public brief

Topic tags
Python
Storage & state

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJul 2025–May 2026

Implement a Quota-Aware Cloud File Store

Process a sequence of string commands against a flat cloud-storage namespace. Every command returns one result string.

Public brief

Topic tags
Python
Storage & state
Networking

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodMay 2026

Implement a DNS Resolver with Aliases and TTL

Build an in-memory resolver over A and CNAME records.

Public brief

Topic tags
Python
Storage & state
Communication

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodMay 2026

Implement a Task Manager with Expiration and Historical Views

Tasks are scoped by (user, task_id). Implement creation, mutation, TTL expiration, and snapshots.

Public brief

Topic tags
Python
Data structures
Data / SQL

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–May 2026

Design a Weighted, Checkpointable Data Batcher

Public brief

Topic tags
Python
Concurrency
ML / AI

AnthropicCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–May 2026

Build a Workforce Time and Pay System

Implement employee time tracking, ranking, deferred promotions, and bonus-pay windows. Time is measured in integer ticks.

Public brief

Topic tags
Python
Data structures

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–May 2026

Kth largest value with duplicates counted

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

Public brief

Topic tags
Python
Concurrency
Distributed systems
Storage & state
Data / SQL

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–May 2026

Design Worker and Coordinator Protocols for Distributed Statistics

Public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Fewest inserts to balance brackets

Report how many bracket characters must be inserted anywhere in a parenthesis string to make every prefix and the whole line balanced.

Public brief

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Tightest slice covering a character multiset

Find the shortest contiguous slice of a source string that contains every character of a required multiset with at least the required multiplicity, and return that slice.

Public brief

Topic tags
Python
ML / AI

AnthropicCodingHalf AI-generated

Talk-through codingNo local grader

Reported interview periodOct 2025–Apr 2026

Debug a GRPO Training Step

New public brief

Topic tags
Python
Concurrency

xAICoding

Talk-through codingNo local grader

Reported interview periodNov 2025–Apr 2026

Make a Bank Account Thread-Safe

New public brief

Topic tags
Python
Data structures
Communication

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Resumable Iterators

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

New public brief

Topic tags
Python
Storage & state

xAICoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Apr 2026

In-Memory Database with Expiry and Snapshots

Build an in-memory database in four stages. Each key owns string field/value pairs.

New public brief

Topic tags
Python
Data structures
Storage & state
Networking

xAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026

Token-Bucket State Transitions

New public brief

Topic tags
Python

xAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026

Flatten and Rebuild Nested Values

A nested value contains integer leaves and internal list, tuple, or dict nodes. Dictionaries are traversed in insertion order.

Previous7 of 9Next

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