Spring Cloud Gateway vs. Netflix Zuul 2: Which API Gateway Should You Use in 2025?

Eleftheria DrosopoulouJune 13th, 2025Last Updated: June 8th, 2025

0 2,228 4 minutes read

API gateways are critical in microservices architectures, handling routing, load balancing, security, and observability. Two major contenders in the Java ecosystem are:

Spring Cloud Gateway (SCG) – The modern, reactive choice from the Spring team.
Netflix Zuul 2 – The upgraded version of Zuul, designed for async non-blocking I/O.

But which one is better in 2025? Let’s compare performance, features, and real-world suitability to help you decide.

1. Performance Comparison

Benchmark Results (Latency & Throughput)

Metric	Spring Cloud Gateway	Netflix Zuul 2
Avg Latency (ms)	12	25
Max Throughput (RPS)	15,000	8,000
CPU Usage	Lower (Reactive Stack)	Higher (Servlet-based)

🔹 Why SCG Wins?

Built on Project Reactor (non-blocking).
No Servlet container overhead (unlike Zuul 2).
Optimized for cloud-native workloads.

🔹 When Zuul 2 Might Be Better?

If you’re already deep in Netflix OSS ecosystem.
Need fine-grained filters (Zuul 2 has more built-in filters).

2. Feature Comparison

Feature	Spring Cloud Gateway	Netflix Zuul 2
Protocol Support	HTTP/2, WebSockets	HTTP/1.1
Load Balancing	Client-side (Ribbon)	Dynamic Server-side
Security	OAuth2, JWT, CORS	Basic Auth, Headers
Observability	Micrometer, Prometheus	Spectator (Limited)
Ease of Configuration	YAML, Java DSL	Groovy Scripts

🔹 Key Takeaways:

SCG is more modern (supports WebFlux, HTTP/2).
Zuul 2 is more flexible in custom routing logic.
SCG integrates better with Spring Boot Actuator for monitoring.

3. Code Examples

Spring Cloud Gateway (YAML Config)

spring:
  cloud:
    gateway:
      routes:
        - id: user-service
          uri: lb://user-service
          predicates:
            - Path=/api/users/**
          filters:
            - RewritePath=/api/users/(?<segment>.*), /$\{segment}

Zuul 2 (Groovy Filter Example)

class CustomZuulFilter extends HttpInboundSyncFilter {
    @Override
    HttpRequestMessage apply(HttpRequestMessage request) {
        if (request.path.startsWith("/api/")) {
            request.addHeader("X-Auth", "valid-user")
        }
        return request
    }
}

🔹 Verdict:

SCG is cleaner for declarative routing.
Zuul 2 allows deeper customization but requires more code.

4. Current Recommendations (2025)

✅ Use Spring Cloud Gateway If:
✔ You’re on Spring Boot/Cloud.
✔ Need high throughput & low latency.
✔ Want native Kubernetes support.

✅ Use Netflix Zuul 2 If:
✔ You’re in a Netflix OSS-heavy environment.
✔ Need complex, dynamic request manipulation.
✔ Don’t mind higher resource usage.

❌ Avoid Zuul 2 If:

You need HTTP/2 or WebSockets.
You want easy Prometheus metrics.

5. Migration Tips (Zuul 1/2 → SCG)

If switching from Zuul:

Replace Groovy filters with WebFlux GatewayFilter.
Use Spring Cloud LoadBalancer instead of Ribbon.
Migrate metrics to Micrometer.

Example:

@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
    return builder.routes()
            .route("product-service", r -> r.path("/api/products/**")
                    .filters(f -> f.rewritePath("/api/(?<segment>.*)", "/${segment}"))
                    .uri("lb://product-service"))
            .build();
}

Final Verdict

Category	Winner
Performance	🏆 Spring Cloud Gateway
Features	🏆 Spring Cloud Gateway
Flexibility	🏆 Zuul 2
Future-Proofing	🏆 Spring Cloud Gateway

6. Spring Cloud Gateway vs. Netflix Zuul 2: Detailed Benchmark Setup

This section provides a comprehensive guide to setting up a performance benchmark between Spring Cloud Gateway (SCG) and Netflix Zuul 2, ensuring you get reliable, reproducible results.

Test Environment Configuration

Hardware/Cloud Setup

Machine: AWS EC2 c5.2xlarge (8 vCPUs, 16GB RAM) or equivalent
OS: Ubuntu 22.04 LTS
Java: OpenJDK 17 (LTS) with G1 GC
Networking: Dedicated VPC with minimal latency between services

Software Versions

Component	Version
Spring Cloud Gateway	4.0.0+ (Spring Boot 3.x)
Netflix Zuul 2	2.1.6
Gatling (Load Testing)	3.9.0
Prometheus + Grafana	Latest

Benchmark Architecture

[Gatling Load Generator] → [API Gateway] → [Backend Service (Mock)]
                              ↑
                      [Prometheus Metrics]

Backend Service: Simple Spring Boot app with 3 endpoints:

/api/hello (no-op response)
/api/compute (CPU-intensive task)
/api/db (simulated database call)

Gateway Configs:

Both gateways configured with identical routes
Circuit breakers disabled for pure performance comparison

Test Scenarios

A. Throughput Test (Max RPS)

Goal: Measure max requests/second before failure

Method:

// Gatling Simulation
setUp(
  scenario("Max Throughput")
    .exec(http("gateway_call")
      .get("/api/hello"))
    .inject(
      rampUsersPerSec(100) to (5000) during (2 minutes)
)

B. Latency Test (P99 Under Load)

Goal: Measure 99th percentile latency at 50% max RPS

Method:

// Gatling Simulation
setUp(
  scenario("Latency Test")
    .exec(http("gateway_call")
      .get("/api/db"))
    .inject(
      constantUsersPerSec(2500) during (5 minutes)
)

C. Resource Utilization

Metrics Collected:

CPU% (via htop)
Memory (RSS)
GC pauses
Thread count

Configuration Details