Sidecar
A helper process that runs alongside an application to provide capabilities like proxying, logging, metrics, or security without changing app code.
Definition
A sidecar is a helper process deployed alongside an application, usually in the same deployment unit, to provide a capability without changing the application code.
Common examples:
- a proxy that handles routing, TLS, retries, or policies
- log shipping and metrics collection agents
- security agents (mTLS, policy enforcement)
Why sidecars exist
Sidecars are a way to standardize operational behavior (networking, observability, security) across many services, even if the services are written in different languages.