How We Built Our API Marketplace: From Tools to Endpoints

We recently launched our API marketplace, exposing 10 of our most popular tools as programmatic endpoints. Here is how we built it.

The Architecture

Each API endpoint follows the same pattern: validate the API key, check rate limits, process the input, and return the result with timing data. The processing functions are the same ones used by the browser tools, extracted into server-side handlers.

API Key Management

Keys are generated with crypto.randomBytes(32) and prefixed with dsk_ for easy identification. Keys are stored hashed in the database. The full key is shown exactly once during creation — we never store or display it again.

Rate Limiting

Free users get 100 requests per day. Premium users get 10,000. We track usage per key with a daily reset at midnight UTC. The counter resets by comparing the date of the last request — if it is a different calendar day, the count resets to zero.

Available Endpoints

We started with 10 tools: JSON format/minify, Base64 encode/decode, URL encode/decode, SHA-256/MD5 hashing, and camelCase/snake_case conversion. Each accepts a simple { "input": "your data" } body and returns { "result": "...", "processingTimeMs": 1.2 }.

What's Next

We are adding more endpoints based on API usage data. JSON Path evaluation and YAML-JSON conversion are the most requested additions.