15:I[981,["658","static/chunks/658-a698693f56d0116a.js","183","static/chunks/183-6beeeb801c274aaa.js","474","static/chunks/app/%5Btype%5D/layout-631c4730b83c8223.js"],"Posts"] 16:T590,I built Feistly to hide auto-increment IDs in URLs with tamper detection.

Most ID obfuscation libraries (Hashids, Sqids, Optimus) are reversible encodings. If you know the algorithm, you can decode tokens or manipulate them without the server detecting it. Feistly uses a Feistel cipher with HMAC-SHA256 to provide:

- Tamper detection: Modified tokens fail validation - Domain separation: User ID 100 and Order ID 100 generate different tokens with the same key - Format-preserving encryption: 64-bit input to 64-bit ciphertext, deterministic

The tradeoff is speed. Feistly does ~60K ops/sec vs millions for Hashids, but for most web apps database queries are the bottleneck anyway.

Example:

  const feistly = new Feistly({ masterKey: process.env.KEY });
  const token = feistly.encrypt("user", 12345); // "7nX4kP2mQ"
  feistly.decrypt("user", token); // "12345"

GitHub: https://github.com/jundev76/feistly npm: https://www.npmjs.com/package/feistly

Zero dependencies (Node.js crypto only), TypeScript native, includes benchmarks.

Feedback welcome – is this solving a real problem or is it overengineering?17:T516,I’m neither outraged nor panicking

I’m fine if 100% of my code is actually from Claude

Most of the time, I like to use Claude Code to make targeted changes along with the tests. I try the feature, notice issues with the change, and clarify with better tests along the way.

Occasionally I give it a more ambitious task, but the variance increases, and much depends on whether I’ve given the right guardrails. Like recentl

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