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Lessons (40)

• Clean Error Handling

  … validate first, happy path last. - Custom error classes make handling precise. - One central error handler per app. - Prefer …

• Serverless Architecture

  … Taking a taxi means you pay only for the trips you take , and someone else handles the car …

• Go Web Services with Gin

  … return t, nil } // handler side: map domain errors to HTTP status codes in ONE place func writeError(c …

• Event-Driven Architecture

  … E) = Promise<void ; class EventBus { private handlers = new Map<string, Handler<any [] (); on<E extends { type: string } (type …

• Serverless: Lambda and API Gateway

  … Your handler must handle the same event more than once without creating duplicate charges, emails, or records. Use …

• Node.js and Express

  … connections on one thread, then Express step by step: routing, the middleware pipeline, validation, async error handling, project …

• Event-Driven Patterns, Step Functions and Reliable Lambdas

  … make handlers idempotent , so running twice gives the same result as running once. text handler(event): validate(event …

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

  … Each handler either handles the request or passes it on. js // Express middleware IS a chain of responsibility …

• NestJS Core Concepts

  … middleware → guards → interceptors → pipes → handler → interceptors → filters on error. - Use a global ValidationPipe with DTOs, guards for auth …

• How a Web Request Works

  Follow one click from the browser to the server and back, through DNS, TCP, TLS, HTTP, load balancers …

• AWS Messaging: Queues, Topics and Events

  … consumers share processing, with retry and duplicate handling SNS A topic: one message can notify many subscribers EventBridge …

• API Gateway, BFF & Service Discovery

  … one entry point for all clients, routing each request to the right microservice and handling shared concerns on …

• Vertical Slice Architecture & the Modular Monolith

  … touches one folder instead of five. A slice = one request, top to bottom Each slice handles one use …

• AI Evaluation, Safety, and Security

  … and appropriate handling of private information. Score important dimensions separately rather than hiding tradeoffs in one average. Automated …

• React Hooks in Practice

  … a slightly stale value while the new one renders useActionState Handle form actions: pending state, result, errors useOptimistic …

• Developer Learning Plan and Document-Assistant Capstone

  … handle missing answers Week 7 Evaluation and authorized tools Add a failure suite and a read-only tool …

• Rust: Types, Errors and Concurrency

  … compile down to loops as fast as hand-written ones. rust let revenue: u64 = orders .iter() .filter( o …

• JavaScript Essentials: Event Loop, Closures & this

  … one thing at a time, like a chef working alone in a kitchen. So how does it handle …

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

  … Command 🧾 Analogy: A waiter writes your order on a ticket. The ticket can be queued, handed to …

• Consumers & Consumer Groups

  … Alert on lag that keeps growing. Tools: Burrow, Kafka UI, Prometheus exporters. Handling failures: retries and dead-letter …

• What to Learn in AI, and in What Order

  … measurement What to build while learning Follow these hands-on lessons alongside the conceptual path: - [Python and math …

• Health Checks and Scaling

  … A cluster autoscaler (or Karpenter on AWS) can add nodes if those pods have nowhere to run. Remember …

• Frontend Testing Strategy

  … Your components, hooks and data libraries run for real; only the server is fake. ts // mocks/handlers.ts …

• Async JavaScript: Promises, async/await and Node's Event Loop

  … a flat chain, one error handler readUser(id) .then((user) = readOrders(user.id)) .then((orders) = console.log(orders …

• Hash Maps & Sets

  … Learn how hashing gives O(1) lookups, how collisions are handled, and the patterns (counting, seen-set, grouping …

• Backend Languages: Node.js, Go, Python & Rust

  … img/backend/languages.svg) How each handles many requests at once This is the most important difference for …

• Go Concurrency: Goroutines, Channels and Context

  … wait on several channels go select { case msg := <-messages: handle(msg) case err := <-errs: return err case <-time …

• Scalable Frontend Architecture

  … A scalable application is not the one with the most folders; it is the one where a developer …

• Atomic Design & Component Libraries

  … structure</summary Small applications may only need feature folders and a handful of primitives. In large applications, feature …

• Design an E-Commerce Checkout

  … Do not release stock or refund based only on a transport timeout. A workflow worker resumes from durable …

• Next.js Rendering: CSR, SSR, SSG, ISR & Server Components

  … They run only on the server , can read the database directly, and send zero JavaScript to the browser …

• Containers at Scale: ECS Deep Dive and EKS

  … Small team, a handful of services ECS on Fargate Cost-sensitive steady workload ECS on EC2 or EKS …

• Python and Math Foundations with Runnable Examples

  … These hand-written vectors demonstrate the calculation without pretending to provide semantic understanding. Count classification mistakes Suppose a …

• Small Functions That Do One Thing

  … a 2-line function used once whose name says less than its body. - Functions with names like handle …

• AWS Databases: Choose the Right One

  … AWS handles hardware, backups, and many maintenance tasks. Put it in private subnets. Allow its port only from …

• State Management (Redux, Zustand, TanStack Query)

  … Redux Toolkit (structured) Redux is the classic, predictable pattern: one store , state changed only by dispatching actions handled …

• Service Communication: Sync vs Async

  … SendEmail Past tense: OrderPlaced , PaymentFailed Receivers Exactly one handler Zero, one or many subscribers Coupling The sender knows …

• Delivery Guarantees: At-Most, At-Least & Exactly Once

  … At-least-once acks=all , idempotence Process, then commit + idempotent handler Most business events ✅ Exactly-once (in Kafka …

• Recursion & Backtracking

  … the tiny one that doesn't open. ![Recursion is like nesting dolls: each call handles a smaller version …

• Sorting Algorithms

  … and learn which one JavaScript's sort() actually uses. The big idea Sorting a hand of playing cards …