Lohnt sich dein eigenes LeetCode?

Build a local coding interview trainer. One repo, single user, no accounts, no cloud, no telemetry. It runs on my machine.

Stack, not negotiable: Python 3.11 with FastAPI on the backend, SQLite through SQLAlchemy, a Vite + React + TypeScript frontend using the Monaco editor, Docker for code execution. Do not add auth. Do not add a hosted judge API.

Problems live on disk, not in the database. Each problem is a folder under ./problems/<slug>/ containing problem.md (the statement), meta.yaml (title, difficulty, topic tags, language stubs) and tests.json (an array of {input, expected} objects, including at least one large case for timing). Write 12 seed problems yourself covering arrays, two pointers, a stack, binary search, BFS on a grid, interval merging, and one small DP. Do not scrape or reproduce LeetCode content.

Execution: POST /api/run accepts {slug, language, code} and runs it in a throwaway Docker container. Only python:3.11-slim and node:20-slim images. Flags: --network none, --memory 256m, --cpus 0.5, --pids-limit 64, read-only root filesystem, non-root user, 5 second wall clock kill. Wrap the submitted function with a harness that feeds each test case and compares output. Return per-test pass or fail, stderr, and runtime in milliseconds. Never execute submitted code outside Docker, not even in dev mode, not even as a fallback.

Store every submission in SQLite: slug, language, code, verdict, runtime, timestamp. I want to diff my third attempt against my first.

Review queue: SM-2 style spaced repetition over solved problems. Correct solve pushes the next due date out, a failure resets it. GET /api/due feeds a Today view that tells me what to redo.

UI, three routes: problem list with difficulty, last verdict and next due date · problem view with statement left, Monaco right, Ctrl+Enter to run, results panel below · stats page with a solve calendar and per-topic pass rate.

Explicitly out of scope: contests, leaderboards, other people's solutions, discussion threads, company tags, languages beyond Python and JavaScript, mobile layout, deployment.

Ship a README with a single make dev command and a .env holding only PORT and DOCKER_HOST. Before you claim it works, prove the sandbox survives an infinite loop, a fork bomb, a 2 GB allocation, and an outbound HTTP request, and paste the output.