Explain advanced distributed rate limiting and traffic shaping architecture in PHP APIs.

Distributed rate limiting controls request throughput across distributed systems to protect infrastructure, enforce fairness, and maintain reliability.

At scale, APIs face enormous traffic variability:

Without traffic controls, systems collapse under overload.

Rate limiting strategies:

Simple counters per interval.

Problem: Boundary spikes.

More accurate rolling limits.

Tokens replenish gradually. Supports bursts.

Smooth traffic flow.

Dynamic limits based on system health.

Traffic shaping concerns:

Prevent noisy neighbors.

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