Intermediate everything in DevOps & Cloud, page 4
Designing a cache health dashboard
Hit ratio, latency, memory and evictions, connections and saturation, with stat panels for current state and time-series for trends.
Correlating logs, metrics, and traces
Propagate a trace and span ID through context, stamp it on logs and metric exemplars, then pivot metric to trace to logs.
Prometheus histogram versus summary
Histograms expose bucket counts and let you compute aggregatable quantiles at query time; summaries compute fixed quantiles per instance that cannot be combined.
High cardinality in time-series databases
Each combination is a separate series consuming memory and index; manage by avoiding unbounded labels and bucketing values.
Redesigning a high-cardinality request metric
Cardinality is unique label combinations; user_id and raw path are unbounded; redesign by dropping user_id and templating the path.
Trace context and propagation across services
Trace context bundles trace ID, span ID, and flags; propagated via headers like W3C traceparent so each service extracts and continues the trace.
OpenTelemetry API, SDK, and Collector
API defines vendor-neutral instrumentation, SDK implements and exports it, Collector receives, processes, and routes telemetry to backends.
Handling planned maintenance in SLOs and error budgets
Either charge maintenance to the error budget or formally exclude it via a maintenance window; each trades honesty against fairness.
Defining SLOs for a new critical service
Start from user journeys, pick SLIs, involve product, engineering, and business stakeholders, set realistic targets iteratively.
Diagnosing a healthy p50 but breaching p99
One percent of requests are slow, hurting power users and fan-out calls; investigate GC, locks, contention, cold caches, retries.
Black-box vs white-box monitoring for legacy apps
Black-box probes from outside, white-box reads internal state; start black-box for fast user-facing signal.
How does distributed tracing work?
Trace ID ties one request together, span IDs are individual operations, context propagates via headers.
Structured vs unstructured logging: why it matters
Unstructured logs are free-text lines hard to parse; structured logs are machine-readable key-value or JSON records; structure enables reliable querying…
Why use latency percentiles over the average?
Averages hide the tail and are skewed by outliers, so most users can suffer while the mean looks fine; use percentiles; prioritize p99 when tail users are high-value or fan-out…
What makes a blameless postmortem effective?
Cover summary, impact, timeline, root cause, action items; explain blameless means focusing on systemic causes so people report honestly.
How do you find and eliminate toil systematically?
Inventory and measure toil via time tracking or ticket analysis, prioritize by frequency times cost versus automation effort, automate highest-ROI items, measure success…
Error budget exhausted early: what now?
Invoke the error budget policy, shift focus from features to reliability, prioritize stability work, analyze what burned the budget.
How do you set SLOs for a service from scratch?
Identify critical user journeys, pick SLIs that reflect user happiness, measure current performance, set achievable targets with buffer, iterate.
Normalization of Deviance
Normalization of deviance is the gradual process by which unsafe practices become accepted as normal because they have not yet caused a visible failure. Each tolerated shortcut lowers the bar, eroding safety margins until a catastrophe finally results.
Hiring for SRE
Hiring for SRE seeks engineers who blend software-development skill with systems and operations depth, plus strong debugging and incident temperament. The hardest part is finding people who can both write automation and reason about failure at scale under…
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