A service mesh adds a dedicated layer (often sidecar proxies) for service-to-service traffic: mTLS, retries, timeouts, and observability. It’s worth it when you have many services and need consistent networking/security controls, but it adds operational complexity.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "what-is-a-service-mesh-and-when-is-it-worth-usin"
function explain() {
// Start from the core idea:
// A service mesh adds a dedicated layer (often sidecar proxies) for service-to-service traff
}