Explain advanced rate limiting and distributed throttling architectures in PHP APIs.

Rate limiting protects APIs from abuse, overload, and resource exhaustion using distributed throttling algorithms.

Modern APIs must defend against:

Rate limiting ensures fair resource allocation.

Core algorithms:

Simple counters per interval.

Problems:

Tracks rolling time intervals.

Tokens refill over time. Allows bursts while maintaining averages.

Smooths traffic flow.

Distributed rate limiting challenges:

Multiple API nodes require centralized coordination.

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