Code RoomResumable file upload endpoint
HardPrep Room Coding #4260

Resumable file upload endpoint

Vibe & agenticAlgorithms & data structuresSenior–Staff~30 min

Greenfield: you're directing an AI agent to build a resumable file-upload endpoint in TypeScript (Node/Fastify) backed by S3 multipart, for files up to 5 GB over flaky mobile connections. Describe how you'd scaffold and sequence the build with the agent: how you pick the chunking protocol (tus vs. S3 multipart vs. roll-your-own), what acceptance criteria you hand it up front, and where you insert review gates. What would a careless one-shot prompt get wrong here?

Implement
plan_missing_parts(total_bytes: int, part_size: int, uploaded_parts: list[int]) → list[int]
Examples
in[15728640,5242880,[1,3]]out[2]
in[11534336,5242880,[]]out[1,2,3]
in[1048576,1048576,[1]]out[]
What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it (tests, edge cases, reading critically), and how you’d re-prompt or decompose to get it right.

0:00 of about 30 min

Vibe & agentic: describe the solution in plain language (or narrate it) and the coach grades your approach.

Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.