API Gateways and Service Meshes are both deal with service communication and traffic control, but they operate in different parts of the architecture and solve distinct problems. Understanding their differences helps in choosing the right tool or knowing when to use both together. Let’s break it down by key aspects:
1. Traffic direction
API Gateway: It manages north-south traffic, i.e., communication between external clients and internal services by acting as the entry point for all inbound API requests.
Service Mesh: They handle east-west traffic, which refers to service-to-service communication inside the application network. It ensures reliable and secure connections between internal microservices.
2. Placement in architecture
API Gateway: Sits at the edge of the network, intercepting and managing all external requests before they reach backend services.
Service Mesh: Operates within the network, with sidecar proxies deployed alongside each service instance, intercepting internal calls.
3. Core responsibilities
API Gateway: Focuses on request routing, rate limiting, authentication, request/response transformation, and API versioning.
Service Mesh: Focuses on service discovery, traffic shaping, retries, circuit breaking, observability, and mutual TLS encryption.
4. Control plane vs data plane
API Gateway: Often includes both control and data planes in a centralised model, where policies are applied through configuration at the gateway level.
Service Mesh: Uses a distributed model where the control plane (e.g., Istio) manages configuration, while data planes (sidecar proxies like Envoy) enforce policies locally.
5. Operational complexity
API Gateway: Simpler to deploy and manage. Typically requires fewer infrastructure changes and is easier to integrate for teams starting out with microservices.
Service Mesh: Requires more infrastructure maturity and operational expertise. It can add complexity, especially in Kubernetes environments, due to its distributed nature.
6. Use cases
API Gateway: Ideal for exposing services to external clients, implementing security at the edge, and managing public or partner APIs.
Service Mesh: Best suited for large, internal service architectures that need fine-grained control over inter-service communication, telemetry, and reliability.
7. Protocol support
API Gateway: Primarily designed for HTTP/HTTPS protocols. Some gateways also support WebSockets, gRPC, and GraphQL, but HTTP-based APIs are the default.
Service Mesh: Often supports a broader range of protocols, including HTTP/HTTPS, gRPC, TCP, and even raw TLS, since it operates at both Layer 4 and Layer 7 of the OSI model.
8. Developer vs platform team ownership
API Gateway: Typically owned and managed by API product teams or platform teams, often with developers directly configuring routing and authentication.
Service Mesh: Usually managed by DevOps or SRE teams, as it’s more infrastructure-heavy and tightly integrated with the service orchestration layer (e.g., Kubernetes).
9. Latency impact
API Gateway: Introduces minimal latency, usually just at the request entry point. Performance impact is predictable and can be optimised through caching and load balancing.
Service Mesh: May introduce more distributed latency due to sidecar proxies being injected alongside every service instance. Requires careful tuning to avoid performance overhead.
10. Observability scope
API Gateway: Provides observability at the entry/exit points of the system, good for understanding how external consumers are interacting with APIs.
Service Mesh: Provides deep observability into internal service calls, retry logic, error rates, and service dependency graphs crucial for debugging distributed applications.