Fix the failing tests. Read the report, find the bug, make it green.
Hand-picked from across the bank. Full challenges, in-browser, no account needed.
Core reasoning on small, self-contained programs.
Navigate code you have never seen before.
Grammars, tokenizers, and tree traversals.
HTTP, routing, and framework internals.
Serialization, schemas, and tooling.
Event loops, task queues, and schedulers.
Real application backends and data flows.
Auth, crypto, and specialized subsystems.