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Lessons (40)

• Imports, Moved Blocks, and Safe Refactoring

  Adopt existing infrastructure, rename resources without recreating them, and remove ownership deliberately. Import brings an existing object under …

• Python Web APIs: FastAPI and Django

  … shared logic (DB sessions, current user, pagination) declared as parameters. python from typing import Annotated from fastapi import …

• Node.js and Express

  … containers, PM2, or node:cluster Unhandled errors Log, exit and let the orchestrator restart the process js import …

• Python Fundamentals

  … return sum(range(n)) Classes and dataclasses python from dataclasses import dataclass, field @dataclass class Product: name: str …

• Frontend Testing Strategy

  … sign up, log in, checkout, payment. ts // e2e/checkout.spec.ts import { test, expect } from "@playwright/test"; test …

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

  … FastAPI python from fastapi import FastAPI, HTTPException from pydantic import BaseModel app = FastAPI() class User(BaseModel): id: int …

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

  … This makes an important design decision visible: checkout business rules do not need to know Stripe's HTTP …

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

  … fullKey }; } } ts // src/storage/storage.module.ts import { Module } from '@nestjs/common'; import { StorageController } from './storage.controller'; import …

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

  … refresh after a CMS edit or mutation import { revalidatePath } from "next/cache"; revalidatePath("/products"); Streaming with Suspense Don …

• Drift, Troubleshooting, and Disaster Recovery

  … Check both cloud inventory and state before deciding whether import is needed. Re-running blindly can create duplicates …

• JavaScript Language Fundamentals

  … js import area, { PI } from "./math.js"; const { readFile } = await import("node:fs/promises"); // dynamic import ES modules …

• Kafka Producers

  … how safe is "sent"? ⭐ The most important producer setting. It controls how many brokers must confirm a write …

• Kubernetes Cluster Architecture, Simply

  … kubectl sends requests here. etcd The cluster’s important notebook: it stores the requested configuration and status. Scheduler …

• Observability: Logs, Metrics & Traces

  … app starts (node --import ./tracing.js server.js) import { NodeSDK } from "@opentelemetry/sdk-node"; import { getNodeAutoInstrumentations } from "@opentelemetry …

• React vs Vue vs Angular

  … bold; } </style Angular (standalone component with signals) ts import { Component, signal, computed } from "@angular/core"; @Component({ selector: "app …

• Vertical Slice Architecture & the Modular Monolith

  … the only file others may import │ ├── domain/ … 🔒 internal │ ├── application/ … 🔒 internal │ └── infrastructure/ 🔒 internal (uses the "ordering" DB schema) ├── catalog …

• AI Evaluation, Safety, and Security

  … Score important dimensions separately rather than hiding tradeoffs in one average. Automated checks are useful for exact formats …

• AWS Security Building Blocks

  … If a customer-managed key is involved, grant the necessary KMS access too. python import json import boto3 …

• Design a Polite Web Crawler

  … oldest queued URL; define recrawl freshness by page importance. Check your understanding Why does one global FIFO queue …

• State Management (Redux, Zustand, TanStack Query)

  … Don't hand-roll that with useEffect + useState . jsx import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"; function …

• Resources, QoS and Scheduling Control

  … Do not set minAvailable equal to replicas , or drains will block forever. PriorityClasses let important pods preempt less …

• Frontend Performance & Core Web Vitals

  … when opened)"] end jsx import { lazy, Suspense } from "react"; const ChartEditor = lazy(() = import("./ChartEditor")); // separate chunk <Suspense fallback …

• NestJS Core Concepts

  … into HTTP responses Handling complaints Modules ts @Module({ imports: [TypeOrmModule.forFeature([Order]), UsersModule], // modules we depend on controllers …

• DRY: Don't Repeat Yourself

  … isValidEmail = (email) = EMAIL PATTERN.test(email); // everywhere else import { isValidEmail } from "./validation/email.js"; if (!isValidEmail(email)) throw …

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

  … data }); worker.once("message", resolve); worker.once("error", reject); }); } Async iteration and streams js import { createReadStream } from "node …

• Python and Math Foundations with Runnable Examples

  … Standardization transforms a value using a training mean and standard deviation. python from statistics import mean, pstdev training …

• D — Dependency Inversion Principle

  … business logic glued to details js import { MySQLDatabase } from "./mysql.js"; import { SendGridMailer } from "./sendgrid.js"; // ❌ OrderService creates …

• What Is Apache Kafka?

  … They don't affect each other. A first taste (Node.js with KafkaJS) js import { Kafka } from "kafkajs …

• Brokers, Replication & Durability

  … Keep it false for important topics.) The controller and KRaft One broker acts as the controller : it tracks …

• TypeScript Essentials

  … true, // turn on all the important checks ✅ "noUncheckedIndexedAccess": true, // arr[i] might be undefined "target": "ES2022", "module": "ESNext …

• Serverless Architecture

  … create an order from an HTTP request import { DynamoDBClient } from "@aws-sdk/client-dynamodb"; import { DynamoDBDocumentClient, PutCommand } from …

• Creational Patterns: How to Make Objects

  … 10 }); js // anywhere.js import { pool } from "./db.js"; // always the same pool The classic class version: js …

• Authentication, Authorization & API Security

  … Never put secrets in a JWT. js import jwt from "jsonwebtoken"; const accessToken = jwt.sign({ sub: user.id …

• Resilience Patterns

  … test calls are let through end note js import CircuitBreaker from "opossum"; const breaker = new CircuitBreaker(callRecommendations, { timeout …

• Advanced TypeScript for Frontend

  … Validate it before it enters application state. Validate unknown data at the boundary ts import { z } from "zod …

• Configuration, Secrets and Storage

  Keep settings out of images, keep sensitive values protected, and keep important data when a pod is replaced …

• TypeScript in Practice

  … It's plain JavaScript at runtime, works with JSON, and needs no import. satisfies : check without widening ts …

• AWS Data Pipelines in Plain Language

  … The important first step is defining the business meaning of a row. Does it represent an order created …

• Batch vs Stream and Data Modeling

  … Do not make the projection the only copy of important state. Question Batch Stream --- --- --- Result needed Hourly/daily …

• Domains, Load Balancers and HTTPS

  … production web server. python from http.server import BaseHTTPRequestHandler, HTTPServer import json class Handler(BaseHTTPRequestHandler): def do GET …