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Lessons (17)

• Scaling, Load Balancing & Rate Limiting

  … Vertical vs horizontal scaling, load balancers, stateless servers, replication, sharding, rate limiting and resilience basics. The big idea …

• API Contracts, Gateways and Security

  … a gateway applies authentication, authorization, rate limits and routing before services enforce resource-level policy](/img/system-design …

• Design a Polite Web Crawler

  … prioritizes freshness/importance and enforces per-host concurrency, rate limits, robots.txt and crawl-delay. Workers fetch, checksum …

• Authentication, Authorization & API Security

  … authentication Weak passwords, no rate limit on login, leaked tokens MFA, rate limiting, short token lifetimes Injection (SQL …

• API Gateway, BFF & Service Discovery

  … http://users-svc:8080 plugins: [jwt-auth, rate-limit: { minute: 100 }] - path: /api/orders service: http://orders-svc …

• Caching & Redis

  … true }); // Rate limit: max 100 requests per minute per user const key = rate:${userId}:${Math.floor(Date.now …

• Design a URL Shortener

  … Protect users with rate limits, phishing scans and destination validation. Disabled links must invalidate quickly.

• Resilience Patterns

  … Timeouts, retries with backoff, circuit breakers, bulkheads, fallbacks and rate limits keep one failure from taking everything down …

• Proxies, APIs and Real-Time Protocols

  … it can terminate TLS, route, cache and rate-limit. A queue is not a WebSocket, and a WebSocket …

• Storage Engines & Database Operations

  … flush Log growth and checkpoint pressure Connection pool Limits scarce DB connections Queueing/starvation when overloaded Connection pools …

• REST API Design

  … on every non-public route (see Authentication & Security ) - [ ] Rate limiting (see Scaling ) - [ ] OpenAPI documentation Key takeaways - Resources are …

• Deploying & Operating Microservices

  … 25% → 100%) to the new version, watching error rates and latency at each step. If metrics get worse …

• Behavioral Patterns II: Chain, Template, Iterator, Mediator, Memento, Visitor

  … 2500 }); // "👔 manager approved" mermaid flowchart LR R[Request] -- H1[Logger] -- H2[Rate limiter] -- H3[Auth] -- H4[Route handler …

• Stacks & Queues

  … Message brokers<br/ RabbitMQ, SQS, Kafka"] Q -- R["🚦 Rate limiting & buffering"] Q -- BFS["🌊 Breadth-first search"] Queue flavours …

• Hash Maps & Sets

  … word frequency, rate limiting per user - Routing : URL path → handler Key takeaways - Hash maps and sets give O …

• How a Web Request Works

  … LR R[Request] -- M["Middleware<br/ logging, auth, rate limit"] -- Rt[Router] -- C[Controller] -- Sv[Service<br/ business …

• Heaps & Priority Queues

  … half + a min-heap for the upper half. - Rate limiters and timers: the next timer to fire sits …