Core Code
Core Code Modern Dev Handbook
REACT Contents
React Fundamentals
React Architecture Overview JSX and Rendering Model Component Design Principles Props and Data Flow State Management with useState Side Effects with useEffect Event Handling Patterns Conditional Rendering Strategies Lists, Keys, and Reconciliation Forms and Controlled Components Component Composition Lifting State and Shared State Basic Routing with React Router Failure Modes in Beginner React Apps
React + TypeScript
Typing Functional Components Typing Props and Children useState and Type Inference useReducer with Type Safety Typing Event Handlers Generic Components Utility Types in React Discriminated Unions for UI State Strict Mode and Null Safety API Response Typing Strategies Form Typing Patterns Avoiding any and Unsafe Casts Type-Safe Context API Failure Modes in React + TypeScript
React Advanced Patterns
Custom Hooks Architecture Context vs Prop Drilling Tradeoffs Compound Components Pattern Controlled vs Uncontrolled Abstractions Render Props and Pattern Alternatives State Machines in React Performance Optimization Playbook Memoization Strategies Code Splitting and Lazy Loading Error Boundaries and Recovery Portal Architecture Large Scale Folder Structure Testing Strategy: Unit and Integration Common React Anti Patterns
React Production
CSR vs SSR vs SSG Hydration and Mismatch Failures Next.js Architecture Overview App Router Deep Dive Authentication Patterns Token Storage Security Role Based UI Control API Integration Patterns Rate Limiting and UI Resilience Frontend Security Checklist XSS in Modern React Observability in Frontend Bundle Optimization Production Incident Playbook
Distributed Systems
Distributed System Fundamentals CAP Theorem in Practice Consistency Models Replication Strategies Leader Election Concepts Consensus Algorithms Overview Event Driven Architectures Message Queues and Delivery Guarantees Idempotency Patterns Saga Pattern Circuit Breakers Backpressure and Flow Control Observability in Distributed Systems Failure Scenarios and Postmortems

Performance Optimization Playbook

Optimize only after measurement. Learn profiling workflow, render root cause isolation, state scoping rules, and incident triage steps that prevent premature optimization and hidden regressions.
On this page

Performance Philosophy

  • Measure before optimizing.
  • Fix root causes, not symptoms.
  • Optimize state boundaries before adding memoization.

Primary Cost Drivers

  • Unstable props causing wide rerenders.
  • State placed too high in the tree.
  • Context value churn.
  • Large lists without virtualization.
  • Expensive computations in render.

Profiling Workflow

  • Use React DevTools Profiler to identify slow commits.
  • Record interaction trace and inspect component flame graph.
  • Check which components rerender and why.
  • Verify if rerender is necessary or accidental.

Isolation Pattern

  • Move state down to the nearest common parent.
  • Split components by responsibility.
  • Introduce memo boundaries only after state scoping is correct.

Large List Strategy

  • Use virtualization for lists above visible viewport size.
  • Ensure stable keys.
  • Avoid inline object creation in list items.

Failure Modes

  • Premature memo usage masking architectural problems.
  • Context updates triggering entire app rerenders.
  • Derived state stored instead of computed.
  • Async effects triggering state loops.

Incident Triage Checklist

  • Which component commits are slow?
  • Which props changed and why?
  • Is state scoped too high?
  • Are memo boundaries placed correctly?
  • Is heavy computation happening during render?
Memoization Strategies →