Bulkheads & Rate Limiting for Resilience
Isolate failures and protect downstream services using bulkhead isolation and the gateway's RequestRateLimiter filter.
Bulkheads & Rate Limiting for Resilience is a free API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Containing the Blast Radius
Circuit breakers stop calls to a broken service, but a flood of traffic to one route can still starve others. Bulkheads and rate limiting keep one busy route from sinking the whole gateway.
The Bulkhead Pattern
Named after a ship's watertight compartments, a bulkhead caps how many concurrent calls a route may have. If one service slows down, only its compartment fills, sparing the rest.
Resilience4j Bulkhead Config
Resilience4j offers a bulkhead that limits concurrent calls per instance.
resilience4j:
bulkhead:
instances:
orders:
maxConcurrentCalls: 20Why Rate Limiting Differs
A bulkhead caps concurrency; a rate limiter caps requests over time. Together they protect both fast bursts and sustained load.
The RequestRateLimiter Filter
Spring Cloud Gateway ships a RequestRateLimiter filter backed by a Redis token bucket. It rejects excess requests with HTTP 429.
filters:
- name: RequestRateLimiter
args:
redis-rate-limiter.replenishRate: 10
redis-rate-limiter.burstCapacity: 20Replenish Rate and Burst
replenishRate is the steady tokens per second; burstCapacity is the most that can be spent in a spike. Burst should be greater than or equal to replenish.
Choosing a KeyResolver
A KeyResolver decides what to limit by, such as user, API key, or IP. Here we limit per user from a header.
@Bean
KeyResolver userKeyResolver() {
return exchange -> Mono.just(
exchange.getRequest().getHeaders()
.getFirst("X-User-Id"));
}Redis Backing Store
The limiter needs Redis so counts are shared across gateway instances. Add the reactive Redis starter.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis-reactive</artifactId>
</dependency>Combining Patterns
Stack resilience filters on a route: circuit breaker first, then rate limiter, so traffic is shaped before reaching a possibly fragile backend.
filters:
- name: CircuitBreaker
args:
name: ordersCB
fallbackUri: forward:/fallback/orders
- name: RequestRateLimiter
args:
redis-rate-limiter.replenishRate: 10
redis-rate-limiter.burstCapacity: 20Graceful Rejection
When the limit is exceeded the client gets 429. You can customize the status, but always return a clear, retryable response so clients can back off.
args:
redis-rate-limiter.replenishRate: 5
statusCode: TOO_MANY_REQUESTSObserving the Limits
Watch metrics for 429 counts and bulkhead rejections. Tune the numbers based on real downstream capacity, not guesses.
Quick Check
What is the core difference between a bulkhead and a rate limiter?
Recap
You added two more resilience tools:
- Bulkheads cap concurrent calls per route
RequestRateLimiteruses a Redis token bucketreplenishRateandburstCapacityshape traffic- A
KeyResolverdefines the limiting key
Combined with circuit breakers, retries, and fallbacks, your gateway degrades gracefully under stress.
Frequently asked questions
Is the “Bulkheads & Rate Limiting for Resilience” lesson free?
Yes — the full text of “Bulkheads & Rate Limiting for Resilience” is free to read here on the web, and the API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) course, upgrade to CoddyKit PRO.
What will I learn in “Bulkheads & Rate Limiting for Resilience”?
Isolate failures and protect downstream services using bulkhead isolation and the gateway's RequestRateLimiter filter. You practise API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway)?
No prior experience is required. API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Bulkheads & Rate Limiting for Resilience” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) lesson?
Yes. Every API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Circuit Breakers with Resilience4j
- Retries & Timeouts Configuration
- Error Handling & Fallbacks
- Bulkheads & Rate Limiting for Resilience