Rate Limiting and Cost Control

The Claude API has rate limits: requests per minute (RPM) and tokens per minute (TPM). Exceeding either limit returns a 429 error. Production applications must implement rate limiting on the client side to stay below the API limits and handle 429 errors gracefully when they occur. The SDK's built-in retry logic handles transient 429 errors, but sustained over-limit traffic requires client-side throttling.

The implementation pattern: use a token bucket or sliding window rate limiter. Track your requests and tokens per minute. When approaching the limit (80% of quota), slow down new requests. When at the limit, queue requests and process them as capacity becomes available. For batch workloads, calculate the total token budget before starting: (number of requests) x (average tokens per request) x (cost per token) = total cost. If the total exceeds your budget, reduce the batch size or use the Batch API for the 50% discount.