Distributed Locks & Redlock

Coordinates exclusive access to shared resources across distributed microservices using multi-master Redis quorums and monotonically increasing fencing tokens.

STAFF ENGINEER TAKEAWAY: Never rely solely on TTL locks without fencing tokens — garbage collection pauses or network freezes can cause silent dual-master split-brain writes.

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More Topics in 6. Advanced Concepts

🚦Rate Limiting & Traffic Throttling

Controls the rate of incoming network traffic to protect services from abusive traffic, scraping, DDoS attacks, and resource starvation.

🪣Token Bucket Rate Limiting Algorithm

A bucket holds up to B tokens and refills at a constant rate R tokens/sec. Each incoming request consumes 1 token. If no tokens remain, requests are dropped.

💧Leaky Bucket Rate Limiting Algorithm

Requests enter a FIFO queue bucket. The bucket leaks requests out to the backend at a strictly constant smooth rate, smoothing out spiky traffic.

🪟Sliding Window Log & Counter

Tracks request timestamps in a sorted set (Redis ZSET) to compute precise request counts within any rolling 60-second window, eliminating boundary burst bugs.