Lesson · Backend Security · Advanced
API Abuse Prevention Explained
Learn API abuse prevention for backend systems, including rate limits, authentication signals, quotas, bot patterns, logging, errors, and gateways.
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Lesson · Authentication · Intermediate
Cookie Security Checklist
Use this backend cookie security checklist for HttpOnly, Secure, SameSite, CSRF, session rotation, prefixes, expiration, domains, and testing.
Lesson · Authentication · Advanced
API Authentication Best Practices
Learn API authentication best practices, including tokens, API keys, OAuth, mTLS, sessions, gateways, rotation, scopes, errors, and logging.
Lesson · Authentication · Beginner
Cookie vs Token Authentication
Compare cookie and token authentication for backend apps, including sessions, JWTs, CSRF, XSS, storage, CORS, mobile clients, and API tradeoffs.
Lesson · Authentication · Intermediate
CORS Preflight Explained
Learn how CORS preflight requests work, including OPTIONS handling, allowed methods, headers, credentials, caching, errors, and backend mistakes.
Lesson · Authentication · Beginner
OAuth Client Credentials Flow Explained
Learn the OAuth client credentials flow for service-to-service APIs, including clients, secrets, scopes, tokens, rotation, and security risks.
Lesson · Authentication · Beginner
OAuth Scopes Explained
Learn OAuth scopes for backend APIs, including permissions, consent, least privilege, access tokens, naming, validation, and common mistakes.
Lesson · Authentication · Beginner
Service Accounts Explained
Learn service accounts for backend systems, including machine identity, API access, least privilege, secrets, rotation, audit logs, and risks.
Lesson · Backend Security · Advanced
Security Event Logging Explained
Learn security event logging for backend systems, including auth events, API abuse signals, safe metadata, alerting, retention, and mistakes.
Lesson · Backend Security · Advanced
Audit Logs Explained for Backend Systems
Learn what audit logs are in backend systems, including actor, action, resource, timestamp, metadata, retention, privacy, and investigation workflows.
Lesson · API Design · Advanced
API Pagination Metadata Best Practices
Learn how to design pagination metadata for REST APIs, including pageInfo, cursors, hasNextPage, limits, totals, links, sorting, and compatibility.
Lesson · System Design · Beginner
Database Connection Pooling Explained
Learn database connection pooling for backend systems, including pool size, timeouts, leaks, max connections, queues, monitoring, and common mistakes.
Lesson · Java Collections · Beginner
HashMap Collision Handling Explained
Learn how HashMap collision handling works in Java, including buckets, hashCode, equals, tree bins, load factor, bad keys, and performance.
Lesson · System Design · Beginner
Database Migration Rollback Explained
Learn database migration rollback strategies, including backward-compatible changes, expand-contract migrations, backups, deploy order, and recovery plans.
Lesson · Java Collections · Beginner
Java equals and hashCode Explained
Learn Java equals and hashCode contracts, why they matter for HashMap and HashSet, common mistakes, records, mutability, and testing.
Lesson · Authentication · Advanced
Least Privilege Explained for Backend Developers
Learn the principle of least privilege for backend systems, including users, services, API keys, database roles, cloud permissions, and operational tradeoffs.
Lesson · System Design · Beginner
N+1 Query Problem Explained
Learn the N+1 query problem in backend apps, including ORM loading, SQL examples, eager loading, batching, joins, query counts, and fixes.
Lesson · API Design · Beginner
JSON Schema vs OpenAPI Schema
Compare JSON Schema and OpenAPI Schema for backend API contracts, including validation, documentation, examples, tooling, and compatibility.
Lesson · Algorithms · Beginner
Prefix Sum Algorithm Explained
Learn prefix sums with Java examples, range-sum queries, subarray patterns, difference arrays, complexity, and when preprocessing is worth it.
Lesson · API Design · Beginner
REST API Design Checklist
Use this REST API design checklist to review resources, methods, status codes, errors, pagination, idempotency, versioning, auth, and OpenAPI docs.
Lesson · Backend Security · Advanced
Secret Management Explained for Backend Developers
Learn secret management for backend apps, including environment variables, secret stores, rotation, least privilege, logging risks, and deployment workflows.
Lesson · Algorithms · Beginner
Sliding Window Algorithm Explained
Learn the sliding window algorithm pattern with Java examples, fixed windows, variable windows, two pointers, complexity, and common mistakes.
Lesson · API Design · Advanced
Spring Boot REST Controller Explained
Learn Spring Boot REST controllers, including @RestController, request mappings, DTOs, validation, status codes, error responses, and testing.
Lesson · Algorithms · Beginner
Two Pointers Algorithm Explained
Learn the two pointers algorithm pattern with Java examples for sorted arrays, pairs, partitions, linked lists, complexity, and common mistakes.
Lesson · Authentication · Advanced
API Key Design Best Practices for Backend APIs
Learn practical API key design best practices, including key format, prefixes, hashing, scopes, rotation, rate limits, audit logs, and safe storage.
Lesson · Authentication · Beginner
API Key vs OAuth Token: Practical Backend Differences
Compare API keys and OAuth tokens for backend APIs, including identity, scopes, rotation, expiration, user context, service access, and security tradeoffs.
Lesson · Java Collections · Beginner
HashSet vs TreeSet in Java
Compare HashSet and TreeSet in Java by ordering, uniqueness, contains performance, null handling, memory cost, and practical backend use cases.
Lesson · Authentication · Beginner
MFA Explained for Web Apps
Learn how multi-factor authentication works in web apps, including TOTP, WebAuthn, backup codes, recovery flows, step-up checks, and backend tradeoffs.
Lesson · Authentication · Beginner
Password Hashing Explained for Backend Developers
Learn password hashing basics for backend systems, including salts, slow hashes, peppers, verification, resets, storage risks, and common mistakes.
Lesson · API Design · Beginner
OpenAPI Explained for Backend Developers
Learn how OpenAPI describes REST APIs, including paths, operations, schemas, examples, auth, versioning, code generation, and contract review.
Lesson · API Design · Beginner
PUT vs PATCH in REST APIs
Compare PUT and PATCH in REST APIs, including replacement vs partial updates, idempotency, validation, status codes, and backend implementation choices.
Lesson · Authentication · Beginner
RBAC vs ABAC: Access Control Models Explained
Compare RBAC and ABAC for backend authorization, including roles, attributes, policies, ownership checks, tenant context, and practical tradeoffs.
Lesson · Authentication · Beginner
Refresh Token Rotation Explained for Backend Developers
Learn how refresh token rotation works, why reuse detection matters, and how backend teams can design safer token refresh, logout, and revocation flows.
Lesson · Java Collections · Advanced
Queue vs Deque in Java
Compare Queue and Deque in Java, including FIFO queues, double-ended operations, ArrayDeque, LinkedList, stack usage, and practical backend defaults.
Lesson · Authentication · Intermediate
SameSite Cookies Explained for Backend Developers
Learn how SameSite cookies affect browser authentication, CSRF risk, cross-site requests, OAuth redirects, iframes, and backend cookie design.
Lesson · Authentication · Intermediate
Secure HTTP Headers Explained for Backend Developers
Learn practical secure HTTP headers for backend apps, including HSTS, CSP, X-Content-Type-Options, frame protection, referrer policy, and cookie-related limits.
Lesson · Authentication · Beginner
Session Fixation Explained for Backend Developers
Learn what session fixation is, how it affects web authentication, why session rotation matters, and how backend teams can prevent it.
Lesson · Java Collections · Beginner
TreeMap vs HashMap in Java
Compare TreeMap and HashMap in Java by key ordering, lookup complexity, range queries, null handling, memory overhead, and backend use cases.
Lesson · Backend Security · Advanced
Webhook Signature Verification Explained
Learn how webhook signature verification works, including HMAC headers, raw request bodies, timestamps, replay protection, secret rotation, and safe failures.
Lesson · Authentication · Advanced
API Gateway Explained
Learn what an API gateway does in backend architecture, including routing, authentication, rate limiting, observability, and tradeoffs.
Lesson · System Design · Intermediate
Background Jobs Explained
Learn how background jobs work in backend systems, including queues, workers, retries, scheduling, idempotency, and monitoring.
Lesson · System Design · Advanced
Caching Strategies Explained
Learn common backend caching strategies, including cache-aside, write-through, write-behind, TTLs, invalidation, and cache stampede risks.
Lesson · System Design · Intermediate
Circuit Breaker Pattern Explained
Learn how the circuit breaker pattern protects backend services from cascading failures, with closed, open, and half-open states.
Lesson · Authentication · Beginner
Authorization vs Authentication
Compare authentication and authorization in backend systems, including identity checks, permissions, roles, scopes, sessions, tokens, and API enforcement.
Lesson · Authentication · Intermediate
CORS Explained for Backend Developers
Learn how CORS works for backend APIs, including origins, preflight requests, credentials, allowed headers, cookies, security limits, and common mistakes.
Lesson · System Design · Intermediate
Distributed Locks Explained
Learn what distributed locks are, when backend systems use them, why they are risky, and what safer alternatives to consider.
Lesson · System Design · Beginner
Eventual Consistency Explained
Learn what eventual consistency means in distributed systems, why stale reads happen, and how backend teams design around them.
Lesson · System Design · Beginner
Database Sharding Explained
Learn what database sharding is, when backend systems need it, how shard keys work, and what tradeoffs sharding creates.
Lesson · System Design · Beginner
Database Transactions Explained
Learn what database transactions are, why ACID matters, how commits and rollbacks work, and what backend developers should know.
Lesson · Authentication · Beginner
JWT Claims Explained
Learn common JWT claims for backend authentication, including sub, iss, aud, exp, nbf, iat, jti, scopes, roles, tenant context, and validation mistakes.
Lesson · System Design · Intermediate
Message Queues Explained
Learn how message queues work in backend systems, including producers, consumers, retries, dead-letter queues, ordering, and idempotency.
Lesson · System Design · Advanced
Load Balancing Explained
Learn how load balancing distributes traffic across backend servers, including algorithms, health checks, sticky sessions, and tradeoffs.
Lesson · Authentication · Beginner
OAuth 2.0 vs OpenID Connect
Compare OAuth 2.0 and OpenID Connect for backend developers, including authorization, login, ID tokens, access tokens, scopes, and common mistakes.
Lesson · Authentication · Advanced
REST API Error Handling Best Practices
Learn practical REST API error handling patterns, including status codes, stable error codes, field errors, request IDs, and safe messages.
Lesson · API Design · Intermediate
Retry Patterns Explained
Learn safe backend retry patterns, including exponential backoff, jitter, retry budgets, idempotency, and when not to retry.
Lesson · API Design · Advanced
Webhooks Explained
Learn how webhooks work in backend systems, including event delivery, signatures, retries, idempotency, and common design mistakes.
Lesson · Java Collections · Intermediate
Binary Search Explained
Learn how binary search works, when it applies, common off-by-one mistakes, and how to implement iterative binary search in Java.
Lesson · API Design · Beginner
API Versioning Explained
Learn practical API versioning strategies, including URL versions, header versions, backward compatibility, deprecation, and migration plans.
Lesson · Algorithms · Intermediate
Database Indexes Explained
Learn how database indexes work, why they speed up reads, when they slow down writes, and how backend developers should choose indexes.
Lesson · System Design · Beginner
Optimistic Locking Explained
Learn how optimistic locking prevents lost updates in backend systems using version columns, compare-and-swap updates, and 409 conflicts.
Lesson · Backend Security · Advanced
Rate Limiting in APIs Explained
Learn how API rate limiting works, including fixed windows, sliding windows, token buckets, 429 responses, headers, and backend tradeoffs.
Lesson · Java Collections · Advanced
Top K Elements Explained
Learn common ways to solve top K elements problems with sorting, heaps, and Java PriorityQueue, including complexity tradeoffs.
Lesson · Java Collections · Beginner
Time Complexity of Java Collections
A practical reference for Java collection time complexity, including ArrayList, LinkedList, HashMap, TreeMap, HashSet, and PriorityQueue.
Lesson · Authentication · Intermediate
CSRF vs XSS: Key Differences for Backend Developers
Compare CSRF and XSS attacks for backend developers, including how they work, why cookies and tokens matter, and practical defenses.
Lesson · Authentication · Beginner
OAuth 2.0 Explained for Backend Developers
A backend-focused OAuth 2.0 guide covering roles, authorization code flow, PKCE, scopes, tokens, client credentials, and common mistakes.
Lesson · Authentication · Beginner
Access Token vs Refresh Token
Compare access tokens and refresh tokens in backend authentication, including lifetime, storage, rotation, revocation, and security tradeoffs.
Lesson · API Design · Advanced
Pagination Strategies for REST APIs
Compare offset, cursor, and keyset pagination for REST APIs, including tradeoffs, response shapes, sorting, and backend performance.
Lesson · API Design · Intermediate
Idempotency in APIs Explained
Learn what idempotency means in API design, why retries create duplicate actions, and how idempotency keys protect backend workflows.
Lesson · Authentication · Advanced
REST API Status Codes Explained
Understand the HTTP status codes backend developers use most often in REST APIs, including 200, 201, 400, 401, 404, 409, and 500.
Lesson · Java Collections · Beginner
ConcurrentHashMap Explained
A practical explanation of ConcurrentHashMap in Java, including thread safety, atomic methods, iteration behavior, and common mistakes.
Lesson · Java Collections · Beginner
HashMap Load Factor Explained
Learn what HashMap load factor means in Java, how it affects resizing, memory usage, collision risk, and lookup performance.
Lesson · Java Collections · Advanced
ArrayList vs LinkedList in Java
Compare ArrayList and LinkedList in Java by access patterns, insertion cost, memory overhead, and practical backend usage.
Lesson · Java Collections · Beginner
Big-O Notation Explained for Backend Developers
Learn Big-O notation with practical backend examples, including arrays, hash maps, sorting, nested loops, and database-like thinking.
Lesson · Authentication · Beginner
JWT vs Session Authentication: Practical Backend Tradeoffs
Understand JWT and server-side session authentication, including storage, revocation, scaling, security risks, and common backend use cases.
Lesson · API Design · Beginner
REST vs RPC: How to Choose an API Style
Compare REST and RPC API styles through resources, actions, payload design, caching, versioning, and backend team workflows.
Lesson · Java Collections · Advanced
Java PriorityQueue Explained with Practical Examples
Learn how Java PriorityQueue works, when to use it, how ordering is defined, and common pitfalls around iteration and custom comparators.
Lesson · Java Collections · Advanced
HashMap vs Hashtable in Java: Key Differences
Compare HashMap and Hashtable in Java, including synchronization, null keys, performance, legacy status, and modern alternatives.
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