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Lessons (40)

• D — Dependency Inversion Principle

  High-level business logic should depend on abstractions, not on concrete details like databases or email providers. The …

• Dependencies, Data Sources, and Resource Lifecycle

  Understand the dependency graph, read existing infrastructure, and reason about replacements and lifecycle safeguards. References create a graph …

• Normalization & Denormalization

  … depend on the whole key Rule: be in 1NF, and every non-key column must depend on the …

• Onion Architecture & Clean vs Hexagonal vs Onion

  … at the bottom that everything depends on, or at the edge where it depends on the domain. Key …

• Clean Architecture

  Organise an application in layers so business rules don't depend on frameworks, databases or the web. Follow …

• Resilient Service Calls: Retries, Breakers and Load Shedding

  Keep one slow dependency from turning a small outage into a full-system outage. The problem in context …

• DBMS Foundations, Keys & Normalization

  … Start from functional dependencies, split tables only when the split preserves necessary relationships, and stop when the design …

• Resilience Patterns

  … Fallbacks and graceful degradation When a non-critical dependency fails, degrade instead of erroring: Failed dependency Fallback --- --- Recommendations …

• Python Web APIs: FastAPI and Django

  … raise HTTPException(401, "Invalid token") return user DB = Annotated[Session, Depends(get db)] CurrentUser = Annotated[User, Depends(current …

• Clean Architecture in Depth

  … ports How can a use case save an order without knowing about Postgres? It depends on an interface …

• Timeouts, Retries & Backpressure

  A slow dependency should consume a bounded budget, not create an infinite retry storm. The problem in context …

• NestJS Core Concepts

  … modules, controllers, providers and dependency injection, then the request lifecycle of middleware, guards, interceptors, pipes and exception filters …

• Docker & Containers

  … build stage ---- FROM node:22-alpine AS build WORKDIR /app Copy dependency files first to make good use …

• SOLID at a Glance

  … microwave's buttons. D Dependency Inversion Depend on abstractions , not concrete details. Lamps depend on the socket, not …

• Debug Latency Like an Investigator

  … Inspect queue age, pool acquisition, query plan/locks, pauses, or dependency timing. 4. Apply the smallest reversible mitigation …

• Resilience, Disaster Recovery and Multi-Region Design

  … Pre-provision capacity rather than depending on scaling during an AZ failure. - Use timeouts, retries with exponential backoff …

• Putting AI Systems into Production

  Design dependable model integrations with fallbacks, observability, versioning, cost controls, and human review. The big idea A production …

• I — Interface Segregation Principle

  Don't force code to depend on methods it doesn't use. Split fat interfaces into small, focused …

• HCL, Resource Addresses, and Project Layout

  … References establish dependencies. One directory is one module A common root layout is: text storage-lab/ versions.tf …

• Layered (N-Tier) Architecture

  … 2. Dependencies point down: a layer may use the layer below it, never the one above. 3. Closed …

• Graphs: BFS & DFS

  Graphs model networks like maps, social media and dependencies. Learn how to store a graph and explore it …

• Hexagonal Architecture (Ports & Adapters)

  … In hexagonal, the data layer is just another adapter that depends on the business. When to use it …

• React Hooks in Practice

  … runs before the next effect and on unmount return () = window.removeEventListener("resize", onResize); }, []); // dependency array mermaid flowchart LR …

• Scaling, Load Balancing & Rate Limiting

  … Readiness can include critical dependencies, but keep it fast and define whether a degraded dependency should remove the …

• Drift, Troubleshooting, and Disaster Recovery

  … IDs Use stable configuration keys Dependency cycle Circular references and broad depends on Remove the cycle or separate …

• Concurrency, Resilience & Distributed Workflows

  … A circuit breaker opens after a failure threshold, fails fast while the dependency recovers, then allows a small …

• Cross-Service Data: How to Join Without a Database JOIN

  … Latency is roughly the slowest dependency plus network overhead, and partial failure must be handled. Use parallel calls …

• Backend Design Scenarios

  … How do you stop one dependency from taking everything down?]( 8-one-downstream-service-becomes-slow-and-suddenly …

• Which Pattern Do I Need?

  … LR P1["Creating objects is messy<br/ or depends on conditions"] -- F[Factory] P2["Constructor has too<br …

• Creational Patterns: How to Make Objects

  … they make testing harder (tests share state) and hide dependencies. Prefer creating one instance in your composition root …

• Frontend Security

  … your dependencies A typical frontend app has 1,000+ npm packages . One compromised package can steal data from …

• L6 Production Debugging Casebook

  … A ten-second dependency call cascades into your outage Three controls should stop this from consuming all of …

• Capacity Planning, SLOs and Error Budgets

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

• Neural Networks and Deep Learning

  … The final layer and loss depend on the task: a class probability, a continuous value, or another output …

• Code Profiling

  … Set timeouts, record dependency latency and error rate, and consider parallel work only when the operations are independent …

• Domains, Load Balancers and HTTPS

  … For EC2 routing, the target type depends on how the app is deployed. Pick it to match the …

• Serverless: Lambda and API Gateway

  … Never depend on local memory for durable coordination. Retry behavior depends on the caller API Gateway does not …

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

  … calling every dependency "our architecture". Stripe, an email provider and a customer browser affect your system, but they …

• EC2, Storage and Auto Scaling

  … an ARM machine image requires compatible software and dependencies. A guided single-server web lab This lab creates …

• Microkernel (Plugin) Architecture

  … the only thing plug-ins may depend on Registry Knows which plug-ins exist, their versions, and how …