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Lessons (17)

• ACID, Transactions & Locks

  Make multi-step changes correct with atomic transactions, isolation choices, constraints and short-lived locks. The bank-transfer …

• Debug Latency Like an Investigator

  … Inspect queue age, pool acquisition, query plan/locks, pauses, or dependency timing. 4. Apply the smallest reversible mitigation …

• Transactions, Indexes & Concurrency

  … transactions protect invariants while indexes speed access and locks coordinate writers](/img/database-interviews/transactions.svg) Q8: What …

• Database Indexing & Transactions

  … lock the row (pessimistic locking) sql BEGIN; SELECT seats left FROM flights WHERE id = 42 FOR UPDATE; -- others …

• Time, Consistency and Distributed Transactions

  Reason about clocks, ordering, split brain, locks, CRDTs and transactions without promising impossible global certainty. ![Distributed correctness: clocks …

• Arrays & Strings

  … Because the lockers are side by side and numbered, you can walk straight to locker 42 without opening …

• Storage Engines & Database Operations

  … wait, active connections, transaction age, slow-query fingerprints, lock waits, replica lag, cache hit rate, WAL/checkpoint or …

• Docker & Containers

  … small and secure ---- FROM node:22-alpine WORKDIR /app ENV NODE ENV=production COPY package.json package-lock …

• Serverless Architecture

  … several seconds, depending on runtime and bundle Vendor lock-in Triggers, IAM and managed services are provider-specific …

• Caching & Redis

  … Prefer delete over update. - Guard against stampedes (locks, jitter), penetration (cache "not found") and hot keys. - Redis offers …

• Data in Microservices: Sagas & the Outbox Pattern

  … It exists, but in microservices it's usually avoided: - Every participant is locked while waiting for the slowest …

• Monolith vs Microservices

  … no shared databases, no lock-step deploys.

• What Is Software Architecture?

  … great scale, but complex queries and more vendor lock-in text docs/adr/ ├── 0001-record-architecture-decisions.md …

• Frontend Security

  … ef4444,color: 7f1d1d class C bad - Commit your lockfile and use npm ci in CI. - Run npm audit …

• Choosing an Architecture

  … workloads, event processing, zero-ops Cold starts, limits, lock-in, cost at scale A decision guide mermaid flowchart …

• Vertical Slice Architecture & the Modular Monolith

  … s divided into separate apartments with their own locked doors. Neighbours can't walk into each other's …

• Domain-Driven Design: Tactical Patterns

  … place 2. Design small aggregates Big aggregates cause lock contention and slow loading 3. Reference other aggregates by …