Introduction to Backend Systems

  • High-level understanding of backend systems
  • Request flow from browser to server
  • Network hops, firewalls, routing
  • Client-server communication model
  • Response structure and handling

HTTP Protocol Deep Dive

  • HTTP message structure and format
  • HTTP headers (request, response, representational, general, security)
  • HTTP methods (GET, POST, PUT, DELETE, PATCH, etc.)
  • HTTP status codes and when to use them
  • CORS (Cross-Origin Resource Sharing)
    • Simple requests vs. pre-flight requests
    • CORS headers and configuration
  • HTTP caching mechanisms (ETags, max-age)
  • HTTP versions comparison (1.1 vs 2.0 vs 3.0)
  • Content negotiation between client and server
  • Persistent connections
  • HTTP compression techniques (gzip, deflate, Brotli)
  • HTTPS, SSL/TLS security

API Design and Routing

  • Route mapping (URLs to server-side logic)
  • Components of routes (path parameters, query parameters)
  • Route types:
    • Static routes
    • Dynamic routes
    • Nested routes
    • Hierarchical routes
    • Wildcard/catch-all routes
    • Regular expression-based routes
  • API versioning techniques
  • API deprecation strategies
  • Route grouping benefits
  • Route security
  • Route matching performance optimization
  • RESTful architecture principles
  • REST API best practices
  • OpenAPI/Swagger specification
  • API-first development approach

Serialization and Deserialization

  • Purpose and benefits (interoperability)
  • Text-based formats (JSON, XML, YAML)
  • Binary formats (Protocol Buffers, MessagePack, BSON)
  • Performance comparisons and tradeoffs
  • Implementation across programming languages
  • JSON deep dive:
    • Structure and data types
    • Handling nested objects and collections
    • Mapping to native data structures
    • Common errors (missing fields, null values, date serialization)
    • Custom serialization implementation
    • Error handling
    • Security concerns (injection attacks)
    • Validation before deserialization
    • JSON Schema validation
    • Performance considerations
    • Compression techniques

Authentication and Authorization

  • Authentication types:
    • Stateful vs. stateless authentication
    • Basic authentication
    • Token-based authentication
    • Session-based authentication
    • JWT (JSON Web Tokens)
    • Cookies
  • OAuth 2.0 protocol and OpenID Connect
  • API keys
  • Multi-factor authentication
  • Cryptographic techniques (salting, hashing)
  • Authorization models:
    • ACL (Access Control Lists)
    • RBAC (Role-Based Access Control)
    • ABAC (Attribute-Based Access Control)
  • Security best practices:
    • Secure cookies
    • CSRF and XSS prevention
    • MITM attack prevention
    • Audit logging
    • Obfuscating error messages
    • Rate limiting and account lockout
    • Preventing timing attacks

Input Validation and Transformation

  • Validation types:
    • Syntactic validation (format, pattern)
    • Semantic validation (business rules)
    • Type validation (data types)
  • Client-side vs. server-side validation
  • Failing fast principles
  • Transformation types:
    • Type casting
    • Date format conversion
    • Normalization (case conversion, whitespace trimming)
    • Sanitization (security)
  • Complex validation logic:
    • Relationship-based validation
    • Conditional validation
    • Chain validation
  • Error handling in validation
  • Validation performance optimization

Middleware Architecture

  • Middleware concept and use cases
  • Request lifecycle middleware (pre-request, post-response)
  • Middleware chaining and flow
  • Proper middleware ordering
  • Next function and early exit patterns
  • Common middleware types:
    • Security middlewares (headers, CORS, CSRF)
    • Rate limiting middleware
    • Authentication middleware
    • Logging and monitoring middleware
    • Error handling middleware
    • Compression middleware
    • Body parsing middleware
  • Performance and scalability considerations

Request Context

  • Request-scoped state management
  • Components of request context:
    • Request metadata (method, URL, headers, params)
    • Session and user information
    • Tracking and logging data
    • Custom request-specific data
  • Use cases (authentication, rate limiting, tracing)
  • Timeouts and cancellation signals
  • Best practices and performance considerations

Handlers and Controllers

  • MVC pattern overview
  • Responsibilities of handlers, controllers, and services
  • Code reduction with middleware
  • Centralized error handling
  • Response formatting standards
  • CRUD operations implementation:
    • Creating resources (POST)
    • Reading resources (GET)
    • Updating resources (PUT, PATCH)
    • Deleting resources (DELETE)
  • Pagination implementation
  • Search API design
  • Sorting and filtering implementation
  • RESTful best practices

Database Management

  • Relational vs. non-relational databases
  • Theoretical concepts (ACID, CAP theorem)
  • Querying and joins
  • Database design best practices:
    • Schema design
    • Indexing strategies
    • Normalization and denormalization
  • Optimization techniques:
    • Query optimization
    • Caching strategies
    • Connection pooling
  • Data integrity:
    • Constraints and validations
    • Transactions
    • Concurrency control
  • ORM (Object-Relational Mapping):
    • Benefits and tradeoffs
    • Popular ORM tools
  • Database migrations
  • NoSQL databases:
    • Document stores (MongoDB)
    • Key-value stores (Redis)
    • Column-family stores (Cassandra)
    • Graph databases (Neo4j)
  • Database sharding and replication

Business Logic Layer

  • Role and responsibilities
  • Application layers:
    • Presentation layer
    • Business logic layer
    • Data access layer
  • Design principles:
    • Separation of concerns
    • Single responsibility
    • Open/closed principle
    • Dependency inversion
  • Components:
    • Services
    • Domain models
    • Business rules
    • Business validation
  • Service layer design best practices
  • Error handling and propagation

Caching Strategies

  • Purpose and benefits
  • Caching types:
    • Memory caching
    • Browser caching
    • Database caching
  • Client-side vs. server-side caching
  • Caching strategies:
    • Cache-aside
    • Write-through
    • Write-behind/Write-back
    • Read-through
  • Cache eviction strategies:
    • LRU (Least Recently Used)
    • LFU (Least Frequently Used)
    • TTL (Time To Live)
    • FIFO (First In First Out)
  • Cache invalidation approaches
  • Caching levels:
    • Level 1 (in-memory)
    • Level 2 (distributed)
    • Hierarchical caching
  • Web application caching (static assets, API responses)
  • Database query caching
  • Cache hit/miss ratio optimization

Transactional Emails

  • Use cases and common scenarios
  • Email anatomy:
    • Subject
    • Preheader
    • Body (header, content, CTA, footer)
  • Personalization with dynamic parameters
  • Email templating systems
  • Email delivery services and APIs
  • Tracking and analytics
  • Best practices for deliverability

Task Queuing and Scheduling

  • Use cases:
    • Email sending
    • File processing
    • Third-party API integration
    • Heavy computation
    • Batch processing
  • Scheduling use cases:
    • Database backups
    • Notifications and reminders
    • Data synchronization
    • Maintenance tasks
  • Task queue components:
    • Producer
    • Queue
    • Consumer
    • Broker
    • Backend
  • Task dependencies:
    • Chain dependency
    • Parent-child relationship
  • Task groups for concurrent execution
  • Error handling and retry mechanisms
  • Task prioritization and rate limiting
  • Popular task queue systems (RabbitMQ, Kafka, Redis Queue)
  • Elasticsearch fundamentals
  • Underlying techniques:
    • Inverted index
    • Term frequency and inverse document frequency
    • Segments and shards
  • Use cases:
    • Type-ahead/autocomplete
    • Log analytics
    • Full-text search
  • Index creation and management
  • Search and query types:
    • Basic search
    • Full-text search
    • Relevance scoring
  • Performance optimization:
    • Field mapping (text vs. keyword)
    • Analyzers and tokenizers
    • Boosting
    • Pagination
  • Advanced search patterns:
    • Filtering
    • Aggregation
    • Fuzzy search
  • Kibana integration
  • Best practices

Error Handling

  • Error types:
    • Syntax errors
    • Runtime errors
    • Logical errors
  • Error handling strategies:
    • Fail-safe vs. fail-fast
    • Graceful degradation
    • Error prevention
  • Best practices:
    • Early catching
    • Custom error types
    • Graceful failure
    • Proper logging
    • Stack trace utilization
  • Global error handlers
  • User-facing error handling
  • Monitoring and logging integration
  • Error alerting systems

Configuration Management

  • Purpose and benefits
  • Use cases:
    • Environment-specific settings
    • Sensitive data management
    • Feature flags
  • Configuration types:
    • Static configs
    • Dynamic configs
    • Sensitive configs
  • Configuration sources:
    • Environment variables
    • Command-line flags
    • Static files (JSON, YAML, INI)
  • Best practices
  • Configuration security

Logging, Monitoring, and Observability

  • Differences between logging, tracing, monitoring, and observability
  • Logging types:
    • System logs
    • Application logs
    • Access logs
    • Security logs
  • Log levels (debug, info, warn, error, fatal)
  • Structured vs. unstructured logging
  • Logging best practices
  • Monitoring types:
    • Infrastructure monitoring
    • Application performance monitoring
    • Uptime monitoring
  • Monitoring tools (Prometheus, Grafana)
  • Alerts and notifications
  • Observability pillars:
    • Logs
    • Metrics
    • Traces
  • Log management security and compliance
  • Distributed tracing in microservices

Graceful Shutdown

  • Purpose and importance
  • Use cases (server restarts, scaling, microservices)
  • Signal handling (SIGTERM, SIGINT)
  • Graceful shutdown steps:
    • Signal capture
    • Stop accepting requests
    • Complete in-flight requests
    • Close external resources
    • Terminate application
  • Implementation patterns
  • Best practices

Security Best Practices

  • Common attacks and prevention:
    • SQL injection
    • NoSQL injection
    • XSS (Cross-Site Scripting)
    • CSRF (Cross-Site Request Forgery)
    • Broken authentication
    • Insecure deserialization
  • Secure software design principles:
    • Least privilege
    • Defense in depth
    • Fail secure
    • Separation of duties
    • Security by design
  • Input validation and sanitization
  • Rate limiting
  • Content Security Policy
  • CORS configuration
  • Secure cookies
  • Security monitoring
  • OWASP Top 10 awareness

Scaling and Performance

  • Performance metrics:
    • Response time
    • Resource utilization
    • Throughput
  • Bottleneck identification
  • Caching strategies
  • Database optimization:
    • N+1 query problem
    • Proper joins
    • Lazy loading
    • Indexes
    • Batch processing
  • Memory management:
    • Avoiding leaks
    • Resource cleanup
  • Network optimization:
    • Payload size reduction
    • Compression
  • Performance testing and profiling
  • Code performance best practices
  • Horizontal vs. vertical scaling
  • Load balancing strategies

Concurrency and Parallelism

  • Differences and use cases
  • Concurrency for I/O-bound tasks
  • Parallelism for CPU-bound tasks
  • Concurrency patterns
  • Thread safety
  • Race conditions and deadlocks
  • Synchronization mechanisms
  • Asynchronous programming patterns

File Storage and Management

  • Object storage (AWS S3, Google Cloud Storage)
  • Large file handling:
    • Chunking
    • Streaming
  • Multi-part file uploads
  • File validation and security
  • Content delivery networks
  • File metadata management

Real-time Backend Systems

  • WebSockets
  • Server-Sent Events (SSE)
  • Pub/Sub architecture
  • Real-time databases
  • Scaling real-time systems
  • Implementation patterns
  • Popular frameworks and tools

Testing and Code Quality

  • Testing types:
    • Unit testing
    • Integration testing
    • End-to-end testing
    • Functional testing
    • Regression testing
    • Performance testing
    • Load and stress testing
    • User acceptance testing
    • Security testing
  • Test-driven development (TDD)
  • CI/CD integration
  • Code quality tools:
    • Linting
    • Formatting
    • Static analysis
  • Code quality metrics:
    • Cyclomatic complexity
    • Maintainability index
    • Code coverage
  • Mocking and stubbing
  • Test data management

12-Factor App Methodology

  • Codebase
  • Dependencies
  • Configuration
  • Backing services
  • Build, release, run
  • Processes
  • Port binding
  • Concurrency
  • Disposability
  • Dev/prod parity
  • Logs
  • Admin processes
  • Implementation patterns

OpenAPI Standards

  • Purpose and benefits
  • History (Swagger to OpenAPI)
  • Versions and features
  • Key concepts:
    • API paths
    • Request/response definitions
    • Parameters
    • Schemas
  • Document structure:
    • Metadata
    • Paths
    • Components
    • Security definitions
    • Responses
  • OpenAPI 3.0/3.1 features
  • Tools (Swagger UI, Postman)
  • Best practices
  • API-first development

Webhooks

  • Use cases and benefits
  • API vs. webhook comparison
  • Components:
    • Webhook URL
    • Event triggers
    • Payload
    • HTTP method
    • Response handling
  • Best practices:
    • Signature verification
    • HTTPS usage
    • Quick response
    • Retry logic
    • Logging
  • Testing strategies
  • Real-world examples

DevOps for Backend Engineers

  • Core concepts:
    • Continuous Integration (CI)
    • Continuous Delivery (CD)
    • Continuous Deployment
  • DevOps practices:
    • Infrastructure as Code
    • Configuration management
    • Version control
  • DevOps tools:
    • Docker (containerization)
    • Kubernetes (orchestration)
    • CI/CD pipelines
  • Scaling strategies:
    • Horizontal vs. vertical scaling
  • Deployment strategies:
    • Blue/green deployment
    • Rolling deployment
    • Canary deployment
  • Monitoring and observability in DevOps
  • Incident response and management

Additional Topics (Filling the Gaps)

Microservices Architecture

  • Monolithic vs. microservices
  • Service decomposition strategies
  • Inter-service communication:
    • REST
    • gRPC
    • Message queues
  • API Gateway pattern
  • Service discovery
  • Circuit breaker pattern
  • Distributed transactions
  • Microservices testing
  • Deployment strategies

GraphQL

  • GraphQL vs. REST
  • Schema definition
  • Queries and mutations
  • Resolvers
  • GraphQL tools and libraries
  • Performance optimization
  • Security considerations
  • Versioning approach

Serverless Architecture

  • Function as a Service (FaaS)
  • Serverless frameworks
  • Event-driven architecture
  • Cold start problem
  • State management
  • Serverless databases
  • Cost optimization
  • Limitations and challenges

Data Streaming and Event-Driven Architecture

  • Event sourcing
  • CQRS pattern
  • Stream processing
  • Kafka architecture
  • Event-driven design patterns
  • Idempotency and exactly-once processing
  • Backpressure handling
  • Stream analytics

Internationalization and Localization

  • i18n fundamentals
  • Locale management
  • Date, time, and number formatting
  • Translation management
  • Right-to-left (RTL) support
  • Character encoding issues
  • Best practices

Domain-Driven Design (DDD)

  • Strategic design
  • Tactical patterns
  • Bounded contexts
  • Ubiquitous language
  • Aggregates, entities, value objects
  • Domain events
  • Implementing DDD in backend systems

Service Mesh

  • Concept and benefits
  • Control plane vs. data plane
  • Popular implementations (Istio, Linkerd)
  • Traffic management
  • Security features
  • Observability enhancements
  • Integration with Kubernetes

Blockchain for Backend Developers

  • Blockchain fundamentals
  • Smart contracts
  • Backend integration
  • Web3 APIs
  • Security considerations
  • Performance challenges
  • Use cases for traditional backends

Machine Learning Integration

  • ML model serving
  • Prediction API design
  • Model versioning
  • Feature engineering
  • Online vs. batch prediction
  • ML monitoring
  • A/B testing frameworks

Compliance and Regulations

  • GDPR compliance
  • CCPA/CPRA compliance
  • PCI DSS for payment systems
  • HIPAA for healthcare data
  • SOC 2 compliance
  • Privacy by design principles
  • Data residency requirements
  • Regulatory reporting

Learning Path Recommendations

Beginner Level

  1. Introduction to Backend Systems
  2. HTTP Protocol Deep Dive
  3. API Design and Routing
  4. Handlers and Controllers
  5. Input Validation and Transformation
  6. Database Management (basics)
  7. Error Handling
  8. Testing and Code Quality (basics)

Intermediate Level

  1. Authentication and Authorization
  2. Middleware Architecture
  3. Request Context
  4. Business Logic Layer
  5. Caching Strategies
  6. Logging, Monitoring, and Observability
  7. Security Best Practices
  8. Configuration Management
  9. Serialization and Deserialization
  10. Task Queuing and Scheduling
  11. RESTful APIs and OpenAPI Standards

Advanced Level

  1. Database Management (advanced)
  2. Elasticsearch and Search
  3. Scaling and Performance
  4. Concurrency and Parallelism
  5. Real-time Backend Systems
  6. Graceful Shutdown
  7. File Storage and Management
  8. 12-Factor App Methodology
  9. DevOps for Backend Engineers
  10. Webhooks
  11. Microservices Architecture
  12. GraphQL
  13. Serverless Architecture
  14. Data Streaming and Event-Driven Architecture

Specialized Skills

  1. Domain-Driven Design
  2. Service Mesh
  3. Machine Learning Integration
  4. Blockchain for Backend Developers
  5. Internationalization and Localization
  6. Compliance and Regulations

Resources

  • Books: “Clean Code” by Robert C. Martin, “Designing Data-Intensive Applications” by Martin Kleppmann
  • Online platforms: Udemy, Coursera, Pluralsight
  • Documentation: Official framework docs, MDN Web Docs
  • Open-source projects: Study popular repositories in your chosen language
  • Practice: Build progressively complex projects applying these concepts
  • Communities: Stack Overflow, Reddit (r/webdev, r/programming)
  • Blogs: High Scalability, Martin Fowler’s blog, The Pragmatic Engineer