SRE Observability & Logging 3

Question 1

Which sampling strategy for distributed tracing captures 100% of traces only when an error or high latency is detected?

Accepted Answer

Tail-based sampling

Answer

Tail-based sampling makes the keep/drop decision after the full trace is complete, allowing it to retain traces with errors or high latency.

Question 2

A team implements structured logging in JSON format. What is the primary operational benefit?

Accepted Answer

Machine-parseable fields that enable consistent filtering and alerting

Answer

Structured JSON logs expose consistent, typed fields that log aggregation tools can index and query without fragile regex parsing.

Question 3

What is the role of a 'context propagation' mechanism in distributed tracing?

Accepted Answer

Passing trace and span identifiers across service boundaries in request headers

Answer

Context propagation carries trace context (trace ID, span ID, flags) in request headers so downstream services can join the same trace.

Question 4

Which metric type is most appropriate for tracking the total number of HTTP requests received since service start?

Accepted Answer

Counter

Answer

A counter is a monotonically increasing value ideal for cumulative counts like total requests, errors, or bytes.

Question 5

An SRE needs to detect when a downstream service begins dropping connections silently. Which observability signal is most directly useful?

Accepted Answer

Error rate and timeout metrics instrumented in the client

Answer

Client-side error rate and timeout metrics capture dropped connections from the caller's perspective, where silent failures are most visible.

(SRE) Site Reliability Engineering Foundation Certification Practice Test