Patterns

35 items

System Design Pattern

API & Gatewaysidecarservice-meshproxycross-cuttinginfrastructureintermediate

Sidecar Pattern

Per-service auxiliary processes for cross-cutting concerns

Used in: Istio, Envoy, Linkerd|20 min read

Summary

The Sidecar pattern deploys helper functionality in a separate container alongside your main application container. The sidecar handles cross-cutting concerns like logging, monitoring, configuration, networking, and security without modifying the main application. This enables polyglot architectures (any language gets the same capabilities), consistent infrastructure features across services, and separation of concerns. Service meshes like Istio and Linkerd use sidecars extensively. The pattern trades deployment complexity for operational consistency.

Key Takeaways

Language-Agnostic Features

Sidecar provides capabilities regardless of main app language. Java, Go, Python all get same logging, tracing, mTLS. No need to reimplement in each language.

Separation of Concerns

Application developers focus on business logic. Platform team maintains sidecar. Clear boundary between application and infrastructure.

Transparent to Application

Sidecar intercepts traffic. Application calls localhost, sidecar handles routing, retries, TLS. No code changes needed.

Resource Overhead

Each pod runs additional container. Memory and CPU cost per sidecar. Thousands of pods = thousands of sidecars.

Latency Considerations

Traffic goes through sidecar proxy. Adds milliseconds per request. For high-performance apps, this matters.

Debugging Complexity

Issues could be in app or sidecar. More components to troubleshoot. Need good observability.

Pattern Details

Sidecar Pattern

Common Sidecar Use Cases:

Service Mesh Proxy (Envoy): Traffic management, load balancing, circuit breaking
Log Shipper (Fluentd): Collect and forward logs
Secrets Manager: Inject secrets, rotate credentials
Config Reloader: Watch for config changes, notify app
TLS Termination: Handle certificates, mTLS

Trade-offs

Aspect	Advantage	Disadvantage

Patterns

Horizontal Scaling Pattern

Retry with Backoff Pattern

Replication Pattern

Caching Strategies Pattern

Persistent Connections Pattern

Load Balancing Pattern

Fan-out Pattern

Fan-in Pattern

Circuit Breaker Pattern

Eventual Consistency Pattern

Queue-based Load Leveling Pattern

Bloom Filters Pattern

Time-Series Storage Pattern

Bulkhead Pattern

Batch Processing Pattern

Write-Ahead Log Pattern

API Gateway Pattern

Backend for Frontend Pattern

Sidecar Pattern

Idempotency Pattern

Rate Limiting Pattern

Backpressure Pattern

Pub/Sub Pattern

Strong Consistency Pattern

Conflict Resolution Pattern

Leader Election Pattern

Consensus Protocols Pattern

CQRS Pattern

LSM Trees Pattern

Sharding Pattern

Event Sourcing Pattern

Stream Processing Pattern

Change Data Capture Pattern

Distributed Locking Pattern

Two-Phase Commit Pattern

Sidecar Pattern

Summary

Key Takeaways

Language-Agnostic Features

Separation of Concerns

Transparent to Application

Resource Overhead

Latency Considerations

Debugging Complexity

Pattern Details

Sidecar Architecture

Sidecar Pattern

Implementation

When to Use

Trade-offs

Sidecar Pattern

Summary

Key Takeaways

Language-Agnostic Features

Separation of Concerns

Transparent to Application

Resource Overhead

Latency Considerations

Debugging Complexity

Pattern Details

Sidecar Architecture

Sidecar Pattern

Implementation

When to Use

Trade-offs