🔸 TL;DR

Resilient APIs don’t “just work” — they fail gracefully.

Timeouts, retries, rate limiting, throttling, idempotency keys, circuit breakers and bulkheads are your toolkit to survive latency spikes, dependency failures and traffic storms ⛈️

🔸 WHAT IS API RESILIENCE?

Designing APIs so that when things go wrong (and they will), your system:

▪️ Degrades gracefully

▪️ Protects itself and its dependencies

▪️ Avoids cascading failures

▪️ Keeps a good UX instead of hanging forever

🔸 KEY PATTERNS TO KNOW

🔹 Timeouts ⏱️

▪️ Never wait forever on a downstream service

▪️ Define reasonable timeouts per call (external APIs, DB, message broker…)

▪️ Better a controlled failure than a hanging request

🔹 Retry Mechanism 🔁

▪️ Retry only for transient errors (network glitch, 502, 503…)

▪️ Use backoff (exponential) and a max retry count

▪️ Combine with idempotency to avoid duplicate side effects

🔹 Rate Limiting 🚦

▪️ Limit how many requests a client can send per time window

▪️ Protects your API from abuse and sudden spikes

▪️ Often implemented as “429 Too Many Requests” with headers

🔹 Throttling 🧯

▪️ Similar to rate limiting but from the provider perspective

▪️ Smooths traffic by slowing down or queuing requests

▪️ Protects internal resources from overload

🔹 Idempotency Key 🔑

▪️ Same request + same key 👉 same effect, even if sent multiple times

▪️ Critical for payment, order creation, emails, etc.

▪️ Avoids double charges and duplicated resources when clients retry

🔹 Circuit Breaker ⚡

▪️ When a dependency keeps failing, “open” the circuit and stop calling it

▪️ Return a fallback or an error immediately instead of waiting

▪️ Prevents cascading failures and protects your upstream services

🔹 Bulkhead 🧱

▪️ Isolate resources by pool (per client, per feature, per dependency)

▪️ If one area is overloaded, it doesn’t sink the whole system

▪️ Think: separate thread pools / connection pools / queues

🔸 TAKEAWAYS 💡

▪️ Resilience is a design choice, not a framework checkbox

▪️ Combine patterns: timeout + retry + idempotency + circuit breaker is a classic combo

▪️ Always think in terms of failure scenarios and blast radius

▪️ The goal is not “never fail”, but “fail in a controlled, user-friendly way”

#️⃣ s

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