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Lessons (30)

• Event-Driven Patterns, Step Functions and Reliable Lambdas

  … See [Step Functions error handling](https://docs.aws.amazon.com/step-functions/latest/dg/concepts-error-handling.html …

• Dynamic Programming

  … function climbStairs(n) { if (n <= 2) return n; let twoBelow = 1, oneBelow = 2; for (let step = 3; step …

• Linked Lists

  … steps. Find the middle When fast reaches the end, slow is exactly in the middle. js function middle …

• Code Smells & Refactoring

  … long function, large class, duplication, feature envy, primitive obsession, switch statements. - Tiny steps, run tests, commit, repeat.

• Creational Patterns: How to Make Objects

  … Builder 🍔 Analogy: At a burger counter you build your order step by step: bun → patty → cheese → no onions …

• Small Functions That Do One Thing

  … Write down in plain English each step it performs. Each step is a candidate for its own function.

• Data in Microservices: Sagas & the Outbox Pattern

  … infrastructure, and it must survive crashes: Temporal , AWS Step Functions and Camunda persist saga state for you. The …

• Big-O Notation Made Simple

  … the problem is cut in half every step function binarySearch(sorted, target) { let lo = 0, hi = sorted.length …

• Binary Search

  … At every step, one half is still sorted ; check if the target lies in that half. js function …

• KISS: Keep It Simple, Stupid

  … A light switch does the same job in one step. ![KISS: a light switch beats a Rube Goldberg …

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

  … pass the varying steps as functions (Strategy) instead of subclassing, i.e. composition over inheritance. --- 3. Iterator 📺 Analogy …

• Recursion & Backtracking

  … solution step by step and undoes a step when it leads nowhere. The universal template js function backtrack …

• Neural Networks and Deep Learning

  … convolutional networks have been useful for images, recurrent networks process sequences step by step, and transformers use attention …

• What Is Clean Code?

  … rename a confusing variable, extract a function, delete dead code. Small steps add up. Key takeaways - Clean code …

• DSA Interview Patterns Cheat Sheet

  … Keyword triggers, a decision flowchart, complexity tables and a step-by-step interview routine. The big idea There …

• Two Pointers & Sliding Window

  … Too expensive together? The right person steps left. Too cheap? The left person steps right. They meet in …

• Which Pattern Do I Need?

  … Builder creates step by step . Observer vs Mediator Observer broadcasts one-to-many. Mediator coordinates many-to-many …

• Graphs: BFS & DFS

  … The ripple reaches everything 1 step away, then 2 steps, then 3… BFS explores level by level using …

• Monolith vs Microservices

  … The network is homogeneous. mermaid flowchart LR subgraph InProcess["Monolith"] A1[orders.create] -- "function call<br/ ~0.001 …

• A WhatsApp OTP Is Only Single Use If You Make It So

  … 3. Create the login in the same step (same transaction) whenever you can. If you cannot, record the …

• Service Communication: Sync vs Async

  … with many steps and compensations Simple flows, many independent reactions Tools Temporal, AWS Step Functions, Camunda Kafka, RabbitMQ …

• Node.js and Express

  What Node.js is and how it serves thousands of connections on one thread, then Express step by …

• Serverless Architecture

  … minutes on AWS Lambda, so long jobs need Step Functions, containers or batching Cold starts 100 ms to …

• Trees & Binary Search Trees

  … right · found! Each step throws away half the tree , just like binary search. js function search(node, target …

• React Fundamentals

  … When state changes, React re-renders that component (and its children). jsx import { useState } from "react"; function Counter …

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

  … You get a receipt with a number , step aside, and the cashier serves the next person. When your …

• Structural Patterns: How to Connect Objects

  … each wraps a function and returns a function with the same shape const withLogging = (fn, name) = async (...args …

• C4 Architecture Diagrams: Context, Container, Component and Code

  … It can show classes, interfaces, functions, packages or aggregates, depending on the language and team conventions. Because code …

• Database Indexing & Transactions

  … The check and the update happen as ONE step. Fix 2: lock the row (pessimistic locking) sql BEGIN …

• Practical Lab: S3 File Upload and CloudFront Delivery with NestJS

  … The result is identical. Step 3: allow only this distribution to read the bucket This is the policy …