Cloud & Reliability Basics

Cloud interviews are rarely about vendor trivia. They’re about architecture and operability.

Primitive building blocks

• compute: VMs, containers, serverless
• storage: object, block, file
• databases: relational, key-value, document
• messaging: queues, pub/sub, streams
• networking: VPC, load balancing, DNS

Reliability building blocks

• timeouts and retries (with backoff)
• idempotency
• circuit breaking / bulkheads
• graceful degradation
• rate limiting
• observability (metrics/logs/traces)

SLO-first thinking

• Define user-facing SLOs (latency, availability, freshness)
• Design for the tails (p95/p99)
• Plan for incidents (runbooks, rollback, alerts)

Failure mode you must avoid

Retry storm: dependency slows → callers retry aggressively → dependency gets worse.

Mitigations:

• cap retries
• add jitter
• use timeouts
• implement circuit breakers
• shed load early