Datadog Software Engineer Case Interview: Observability‑First Distributed Service Design and Prod Debugging

This case reflects Datadog’s practical, production‑minded interview style. You will design and troubleshoot a multi‑tenant telemetry pipeline and query service (metrics, logs, traces) with an emphasis on observability, reliability, and customer impact. Format - 5–10 min context: clarify use cases, traffic profile, success criteria; define SLIs/SLOs (e.g., ingest latency, data loss rate, query p95/p99) and error budget. - 35–40 min architecture deep dive: propose APIs and data flow; tagging and high‑cardinality controls; partitioning/sharding strategy; backpressure and queueing; idempotency/deduplication; retries and rate limiting; sampling (head vs tail); storage/retention tiers and rollups; multi‑tenant isolation and RBAC; multi‑AZ/region failover and disaster recovery; cost/performance trade‑offs. - 10–15 min production debugging drill: investigate a spike in dropped spans and elevated ingest p99; describe what dashboards/monitors you’d build, which metrics/logs/traces to inspect, how you’d form and test hypotheses, and immediate mitigations vs longer‑term fixes. - 5–10 min operability and rollout: canaries/feature flags, safe deploys, runbooks, alert quality (signal‑to‑noise), incident response and postmortems. What good looks like - Clear problem framing, crisp diagrams, and numbers‑driven trade‑offs. - Observability‑centric reasoning: using metrics, logs, and traces to detect, triage, and remediate issues. - Ownership mindset: on‑call readiness, blast‑radius control, and customer empathy. - Security and privacy awareness: PII scrubbing, tenant boundaries, and principle of least privilege. Focus areas aligned with Datadog culture - Distributed systems and real‑time data pipelines at scale. - High‑cardinality tagging and query efficiency. - SLO‑driven design and reducing alert noise. - Pragmatic, product‑minded choices over theoretical perfection. Expect no trick puzzles—just realistic production scenarios.