Application Metrics means every service continuously exposes small, cheap, numeric measurements (request latency, error counts, throughput, queue depth, memory, business counters like "claims submitted") to a...
Log Aggregation means every service writes its logs as structured events to stdout or an agent, and a pipeline ships them to one central, searchable, access-controlled store.
Distributed tracing gives every request a single identity (a *trace ID*) that travels with it through every service, queue and database call it touches.
A rate limiter decides, per caller, how many requests the system will accept in a given time (or how many it will process at once) and rejects or delays the rest, usually with HTTP 429 and a Retry-After header.
A Fallback is the "plan B" your service runs when a dependency call fails or is rejected (timeout, open circuit, bulkhead full, 5xx).
Retry & Backoff means that when a call to another service or resource fails with a *transient* error (a network blip, a 503, a throttling response, a deadlock victim), the caller waits a short, growing, randomised...
