What is Sidecar?

The sidecar pattern is a software architecture pattern where a companion application (the 'sidecar') is deployed alongside a primary application. The sidecar enhances or extends the primary application's capabilities without being part of its core logic. This is often used for cross-cutting concerns like logging, monitoring, security, or service discovery. Sidecars promote modularity and separation of concerns, allowing these functionalities to be independently scaled, updated, and reused across different applications.