Search

Lessons (30)

• Message Queues & RabbitMQ

  … The ticket rail is a message queue : - Producer (waiter): puts messages in. - Queue (rail): holds them safely, in …

• Stacks & Queues

  Stacks are last-in-first-out, queues are first-in-first-out. Two simple structures behind undo buttons …

• Proxies, APIs and Real-Time Protocols

  Pick REST, RPC, queues, long polling, WebSockets, TCP or UDP based on the interaction shape. ![Communication choices: reverse …

• Timeouts, Retries & Backpressure

  … deadline budgets, limited concurrency, a queue and explicit overload shedding](/img/system-design-l6/backpressure.svg) One deadline …

• Graphs: BFS & DFS

  … It powers GPS navigation and network routing. (See Heaps & Priority Queues .) Key takeaways - Graph = nodes + edges; directed or …

• Heaps & Priority Queues

  … That's a priority queue , and a heap is the clever data structure that implements it efficiently. Structure …

• JavaScript Essentials: Event Loop, Closures & this

  … call stack, Web APIs, task queues](/img/frontend/event-loop.svg) Part Kitchen analogy Role --- --- --- Call stack The …

• Kafka vs RabbitMQ & the Kafka Ecosystem

  … topic + partition by key Ordering Per queue (with one consumer) Per partition Throughput High (tens of thousands of …

• Trees & Binary Search Trees

  … pre-, in-, post-order (DFS) and level-order (BFS with a queue). - In-order traversal of a BST …

• Flash Sale: 10 Million Buyers, No Oversell

  A queue smooths traffic but does not reserve stock. The durable inventory owner decides the winner atomically. The …

• Debug Latency Like an Investigator

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

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

  … The request became an object . Problem: you want to queue, log, undo or redo operations. js class TextEditor …

• Serverless Architecture

  … JSON.stringify(result) }; }; When to use it ✅ Spiky or unpredictable traffic, event processing (uploads, queues, webhooks), scheduled jobs …

• What Is Apache Kafka?

  … each group has its own offsets Replay old messages ❌ ✅ Rewind the offset Ordering Per queue Per partition Throughput …

• Service Communication: Sync vs Async

  … sync for queries the user waits on, events for state changes, queues for background jobs.

• Scaling & Health Probes

  … Autoscaling The big idea A supermarket opens more checkout lanes when the queues get long, and closes some …

• Design a Reliable Notification System

  … preferences feed priority queues, channel providers and idempotent delivery tracking](/img/system-design-l6/notifications.svg) Create an …

• Time, Consistency and Distributed Transactions

  … Avoid distributed locks where atomic database/queue claiming owns the state. Two-phase commit offers coordinated atomicity but …

• Observability: Logs, Metrics & Traces

  … CPU, memory, queues"] If you only build one dashboard, build this one, per service. Pillar 3: Traces, the …

• Which Pattern Do I Need?

  … algorithms<br/ at runtime"] -- ST[Strategy] P11["Undo / queue / log actions"] -- CM[Command] P12["Behaviour depends on status …

• Premiere-Night Video Streaming

  … cap bitrate, disable previews, or queue sessions. Heartbeat progress to Redis for fast resume and persist asynchronously to …

• Caching & Redis

  … leaderboards, rate limits, queues, sessions.

• Storage Engines & Database Operations

  … checkpoint pressure Connection pool Limits scarce DB connections Queueing/starvation when overloaded Connection pools are a shared budget …

• Arrays & Strings

  … If you need fast adds and removes at both ends, use a queue or deque (see Stacks & Queues …

• DSA Interview Patterns Cheat Sheet

  … n) O(n) O(1) O(1) Stack / queue – O(n) O(1) O(1) Balanced BST O …

• Scaling, Load Balancing & Rate Limiting

  … S5["5️⃣ DB read replicas"] S5 -- S6["6️⃣ Queues for background work"] S6 -- S7["7️⃣ Sharding / split into …

• Hexagonal Architecture (Ports & Adapters)

  … The application core sits in the middle; everything else (web UI, REST API, tests, database, email, message queues …

• KISS: Keep It Simple, Stupid

  … Add microservices, queues and caches when real problems show up, not before. How to practise KISS Ask yourself …

• Clean Error Handling

  … order); } catch (error) { if (error instanceof ConnectionError) return queueForRetry(order); throw error; // …otherwise let it travel up } 💡 Only …

• What Is Software Architecture?

  … and external systems Everyone 2. Container Apps, databases, queues inside the system Developers, ops 3. Component Main modules …