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Lessons (18)

• Flash Sale: 10 Million Buyers, No Oversell

  … The durable inventory owner decides the winner atomically. The invariant Never sell more units than exist. The winner …

• Design an E-Commerce Checkout

  … catalog/search are read paths while inventory, payment and order transitions are owned and idempotent](/img/system-design …

• ACID, Transactions & Locks

  … UPDATE inventory SET available = available - 1 WHERE sku = :sku AND available 0; If zero rows change, inventory was …

• Data in Microservices: Sagas & the Outbox Pattern

  … No central coordinator. mermaid flowchart LR O[Orders] -- OrderCreated I[Inventory] I -- StockReserved P[Payments] P -- PaymentFailed I2 …

• Event-Driven Architecture

  … Orders knows everyone"] O1[Orders] -- reserve I1[Inventory] O1 -- charge P1[Payments] O1 -- email E1[Email] O1 -- track …

• Service Communication: Sync vs Async

  … reserve INV1[Inventory] OR -- 2. charge PAY1[Payments] OR -- 3. ship SHIP1[Shipping] end subgraph Chor["💃 Choreography: dancers …

• Structural Patterns: How to Connect Objects

  … inventory, payment, shipping, email… class CheckoutFacade { constructor({ inventory, payments, shipping, mailer }) { Object.assign(this, { inventory, payments, shipping, mailer …

• Monolith vs Microservices

  … events .- IS[Inventory svc] -- IDB[(inventory DB)] end The trade-offs Monolith Microservices --- --- --- Deploy Everything at once Each …

• Data Structures for Scale

  … Never use a Bloom-filter positive as proof of authorization or inventory ownership.

• Capacity, Availability, Latency and CAP

  … Payments/inventory normally reject uncertain writes; feeds/counters can serve a stale value. CAP is about partitions, not …

• Finding Service Boundaries with DDD

  … OO["Order<br/ lines, status, total"] end subgraph Inventory["📦 Inventory context"] IS["StockItem<br/ sku, quantity, location"] end …

• Timeouts, Retries & Backpressure

  … app work 150 ms Stop before downstream work. Inventory 250 ms Controlled temporary failure. Payment 450 ms Reconcile …

• Behavioral Patterns I: Observer, Strategy, Command, State

  … 99, items: ["book"] }); mermaid flowchart LR S["📢 Subject<br/ orders.emit('order:placed')"] -- O1[📧 Mailer] S -- O2[📦 Inventory …

• SQL vs NoSQL Databases

  … answer complex questions, ACID transactions keep money and inventory correct, and SQL is a universal language. Examples: PostgreSQL …

• Kafka vs RabbitMQ & the Kafka Ecosystem

  … OS -- outbox + CDC T1[(orders.placed)] T1 -- Inv[Inventory svc] T1 -- Pay[Payments svc] Pay -- T2[(payments.completed …

• Deploying & Operating Microservices

  … abc"] -- P["Payments<br/ traceId=abc"] O -- I["Inventory<br/ traceId=abc"] G & O & P & I -- T[("🔎 Tracing …

• Observability: Logs, Metrics & Traces

  … section orders-svc create order :20, 300 section inventory-svc reserve stock :40, 120 section payments-svc charge …

• Domain-Driven Design: Tactical Patterns

  … Tx2 subgraph Tx2["Transaction 2 (moments later)"] I[Inventory aggregate] -- reserve stock I end Repositories: a collection of …