Proxy federal agency API calls through api.data.gov to apply centralized API key management and rate limiting

Verified steps

1. Register a user-facing API key at api.data.gov/signup; the key is a 40-character alphanumeric token passed as the X-Api-Key header or api_key query parameter on all requests routed through the gateway.
2. Use the gateway base URL provided for the specific agency API (e.g., api.regulations.gov, api.grants.gov, api.fueleconomy.gov) rather than the agency's direct endpoint; the gateway handles authentication forwarding and rate limit enforcement.
3. Monitor your current rate limit consumption by inspecting the X-RateLimit-Limit (total allowed) and X-RateLimit-Remaining (requests left in window) headers returned on every response.
4. When X-RateLimit-Remaining approaches zero, implement backoff logic; a 429 Too Many Requests response means the rate window is exhausted. Default limits are typically 1,000 requests per hour for most API key tiers.
5. For agency operators integrating their own API behind api.data.gov, configure the API Umbrella backend via the Agency Manual; you can set custom rate limits per API key, enable or disable API key requirement, and configure analytics.
6. Use the DEMO_KEY (no signup required) only for development testing — it has a rate limit of 30 requests/hour and 50 requests/day and is not suitable for production traffic.