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API Policy

Rate limits, fair usage, and best practices

Rate Limits
To ensure fair access for all users, the following rate limits apply
Free TierDefault
  • 100 requests per minute
  • 1,000 requests per hour
  • 10,000 requests per day
With API KeyEnhanced
  • 500 requests per minute
  • 10,000 requests per hour
  • 100,000 requests per day
Response Headers

Each API response includes headers to help you track your usage:

X-RateLimit-Limit:100
X-RateLimit-Remaining:95
X-RateLimit-Reset:1709568000
X-Request-Id:req_abc123...
X-Trace-Id:trace_xyz789...
X-JA4H:ge20cn12enus_...
Security Requirements

Required

  • All requests must use HTTPS (TLS 1.2+)
  • Valid Content-Type header for POST requests
  • Proper User-Agent identification

Recommended

  • Include X-Request-Id for request correlation
  • Implement exponential backoff for retries
  • Cache responses when appropriate (5-minute TTL)
Best Practices

Error Handling

Always check response status codes and handle errors gracefully:

200 - Success

400 - Invalid request parameters

429 - Rate limit exceeded

500 - Server error (retry with backoff)

503 - USPS API unavailable (fallback rates provided)

Caching Strategy

Rate calculations for the same origin, destination, weight, and dimensions can be cached for up to 5 minutes. Responses include Cache-Control headers to guide your caching implementation.

Idempotency

All rate calculation endpoints are idempotent. Identical requests will return identical results (subject to USPS rate changes). Include X-Idempotency-Key for POST requests to safely retry without duplicate processing.

Available Endpoints
GET/api/healthHealth check
POST/api/v1/rates/calculateDomestic rates
POST/api/v1/rates/internationalInternational rates
GET/api/v1/fingerprintJA4H fingerprint
GET/api/v1/auditRequest traces
GET/api/docsOpenAPI spec

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