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Lessons (40)

• Frontend Testing Strategy

  What to test and how. The testing trophy, unit tests with Vitest, component tests with Testing Library, API …

• Testing, Preconditions, and Policy Checks

  Use validation, lifecycle conditions, Terraform tests, and policy checks to catch different classes of errors. Different checks answer …

• Hexagonal Architecture (Ports & Adapters)

  … Driving vs driven sides, a complete TypeScript example, testing with fake adapters, and how to structure the folders …

• Train Your First Model from Scratch

  … The training-average baseline is 10 minutes, giving test MSE of 37. The trained model's test MSE …

• Code Smells & Refactoring

  … nothing leaves, it just ends up in the right place. mermaid flowchart LR T1["✅ Tests pass"] -- S["Make …

• Machine Learning Fundamentals

  … Estimating a home's sale price is regression. Train, validate, test The training set fits model parameters. The …

• CI/CD and Reviewed Production Changes

  … The test command assumes a maintained test suite and safe test credentials. Tests using apply can create resources …

• Production Capstone and Interview Practice

  Combine modules, isolated environments, remote state, tests, and reviewed delivery in a production-style storage project. Build a …

• Data Preparation and Model Training

  … train on the past and test on a later period. Fit preprocessing steps on training data only, then …

• D — Dependency Inversion Principle

  … new SesMailer(awsConfig), }); // Tests: plain fakes, no network const sent = []; const testService = new OrderService({ orderRepository: { save: async () = {} }, mailer …

• Python Web APIs: FastAPI and Django

  … res = client.post("/tasks", json={"title": "Write tests"}) assert res.status code == 201 assert res.json()["title"] == "Write …

• NestJS Core Concepts

  … process.env.NODE ENV === "test" ? FakeGateway : StripeGateway }, { provide: "APP NAME", useValue: "shop-api" }, { provide: "REDIS", useFactory: async (config …

• Deploying & Operating Microservices

  … own tests and its own pipeline. mermaid flowchart LR C[💻 Commit] -- B["🔨 Build<br/ + unit tests"] -- I["🐳 Docker …

• AI Evaluation, Safety, and Security

  Build representative tests, measure retrieval and model quality, defend against prompt injection, and handle sensitive data responsibly. The …

• Onion Architecture & Clean vs Hexagonal vs Onion

  … infrastructure, UI, tests Implementations of the interfaces, web framework, DB, external APIs SqlOrderRepository , controllers, EF Core / Prisma mermaid …

• Clean Architecture

  … No database, no network, milliseconds per test. js test("rejects duplicate emails", async () = { const userRepository = new InMemoryUserRepository([{ id …

• Clean Architecture in Depth

  … Entities, use cases, input and output ports, presenters, crossing boundaries with DTOs, "screaming" folder structure, testing, and common …

• Go Fundamentals

  … interfaces for behaviour . Table-driven tests go func TestDivide(t testing.T) { tests := []struct { name string a, b …

• Safe AWS Deployments with IaC and CI/CD

  … Deploy through a reviewed pipeline, not from one person’s laptop. mermaid flowchart LR C[Commit] -- T[Tests …

• MVC, MVP & MVVM

  … Keeping these three apart means you can redesign the screen without rewriting the news, and test the producer …

• Multi-Account Strategy, Governance and Security Operations

  … Follow tested session-revocation procedures and verify the relevant policy enforcement. Replacing a security group also does not …

• YAGNI: You Aren't Gonna Need It

  … Clean, tested code is what lets you change safely later. - Do think ahead for decisions that are expensive …

• DRY: Don't Repeat Yourself

  … s]+\.[^@\s]+$/.test(email)) throw new Error("Invalid email"); // profile.js if (!/^[^@\s]+@[^@\s]+\.[^@\s]+$/.test(email)) throw …

• Design System Operations

  … Do not replace native controls unnecessarily, and test keyboard navigation in the final styling—not only in the …

• Rust: Types, Errors and Concurrency

  … listener, app).await.unwrap(); } Testing rust [cfg(test)] mod tests { use super:: ; [test] fn parses valid port() { assert …

• Go Web Services with Gin

  … net/http basics, Gin routes and groups, binding and validating JSON, middleware, a layered project structure, handler tests …

• Design a File Storage Service

  … needs stronger enforcement. How to prove it worked Test interrupted uploads, duplicate completion and revoked sharing. Measure completion …

• Capacity, Availability, Latency and CAP

  … Treat every number as a testable assumption and load-test the real bottleneck. Consistency choices in plain language …

• O — Open/Closed Principle

  … is risky Every time you open a working, tested function to add an else if , you risk breaking …

• Node.js and Express

  … z.enum(["development", "test", "production"]).default("development"), PORT: z.coerce.number().default(3000), DATABASE URL: z.string().url …

• DSA Interview Patterns Cheat Sheet

  … Interviews test whether you can recognise the pattern from the wording, then apply its template. Pick a technique …

• Internals, Upgrades, Resilience and Interview Questions

  … A backup never tested is a hope, not a backup. Service mesh in one paragraph A mesh (Istio …

• What Is Software Architecture?

  … in under a week Testability Can we verify it quickly? Business rules testable without a database Security Is …

• What to Learn in AI, and in What Order

  … 3. Machine learning: Understand features, labels, training, validation, test sets, loss, overfitting, and metrics. Learn how to compare …

• Atomic Design & Component Libraries

  … necessary—dialog, menu, combobox, tabs—use a well-tested headless primitive or fully implement keyboard navigation, focus management …

• Python Fundamentals

  … It's promising, but most production code still assumes the GIL. Testing with pytest python test pricing.py …

• Capacity Planning, SLOs and Error Budgets

  … Load-test peaks and degraded dependency scenarios. Use multi-window budget burn signals to decide when to slow …

• Cost Optimization and the Well-Architected Framework

  … tested recovery Performance efficiency Are we using the right resources? Right-sizing, caching, managed services, load testing Cost …

• Serverless: Lambda and API Gateway

  … You still write, test, secure, and monitor the code; AWS manages the servers. mermaid flowchart LR B[Browser …

• Developer Learning Plan and Document-Assistant Capstone

  … Existing web developers can reuse API, authentication, testing, and deployment skills. Stage Learn Build Completion evidence --- --- --- --- Week 1 …