Containers vs Virtual Machines: Key Differences Explained
Containers share the host kernel through namespaces and cgroups; VMs boot their own OS on a hypervisor. Compare isolation, startup, size and fit.
~6 min readread →
Developer interview notes & guides — Page 1
Focused explanations and longer guides, with worked scenarios, common mistakes and interview exercises across every chapter.
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Showing 1–24 of 746 articles
Script async vs defer vs type=module: Loading Order Explained
When a plain script blocks parsing, why async runs in arrival order and defer in document order, and how module scripts fit, tested in Chrome.
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Abstract Class vs Interface in Java: When to Use Each
Abstract classes share state and constructors; interfaces define capabilities a class mixes in. See what default methods and sealed types change.
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Checked vs Unchecked Exceptions in Java
Checked exceptions must be caught or declared; unchecked ones needn't be. See the compiler rules, the lambda problem and when to use each.
~7 min readread →
HashMap vs ConcurrentHashMap in Java: Key Differences
HashMap isn't thread-safe, synchronizedMap locks every call, and ConcurrentHashMap offers lock-free reads and atomic updates. When to use each.
~7 min readread →
String vs StringBuilder vs StringBuffer in Java
String is immutable, StringBuilder is a fast mutable buffer and StringBuffer adds locks. Why += in a loop is quadratic and which one to use.
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call vs apply vs bind in JavaScript: Differences With Examples
call and apply run a function now with a chosen this; bind returns a new function for later. Covers arguments, borrowing and the listener trap.
~6 min readread →
Callbacks vs Promises vs Async/Await in JavaScript Explained
One task written three ways (callbacks, promise chains, async/await) with error handling, parallel work and the return-await trap, run in Node.
~6 min readread →
localStorage vs sessionStorage vs Cookies: Key Differences
How long each lasts, who can read it, what goes to the server, and why HttpOnly cookies beat localStorage for session tokens when XSS is in play.
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map vs forEach vs for...of in JavaScript: Which Loop to Use
map builds a new array, forEach runs side effects and returns undefined, for...of can break. See sparse arrays, chaining and the parseInt trap.
~6 min readread →
Monolith vs Microservices: Trade-offs and the Modular Monolith
When one deployable beats many services, what microservices cost in latency and availability, and how a modular monolith keeps options open.
~6 min readread →
Redux vs Context API in React: Which One Should You Use?
Context passes a value down the tree; Redux Toolkit manages state with selectors and devtools. Compare re-renders and see where Zustand fits.
~7 min readread →
@Component vs @Service vs @Repository in Spring
All three register a bean through component scanning. Only @Repository adds behaviour: it turns persistence errors into DataAccessException.
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@Controller vs @RestController in Spring Boot
@RestController is @Controller plus @ResponseBody: return values become the response body, not view names. See both styles and the usual bugs.
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Spring vs Spring Boot: What Is the Difference?
Spring Framework provides dependency injection, MVC and transactions; Spring Boot sets it up with starters, auto-configuration and a server.
~6 min readread →
DELETE vs TRUNCATE vs DROP in SQL (PostgreSQL)
DELETE removes chosen rows, TRUNCATE empties a table fast, DROP removes the table. Compare rollback, triggers, identity and locks in Postgres.
~7 min readread →
INNER JOIN vs LEFT JOIN: Differences and the WHERE Trap
INNER JOIN keeps only matching rows; LEFT JOIN keeps every left row and fills gaps with NULL. See counts, anti-joins and the WHERE filter trap.
~6 min readread →
UNION vs UNION ALL in SQL: Duplicates and Performance
UNION removes duplicate rows after combining two queries; UNION ALL keeps every row and skips the sort or hash. Learn when each is correct.
~6 min readread →
REST vs GraphQL: Differences, Trade-offs and When to Use Each
REST exposes resources at URLs; GraphQL lets clients ask for exact fields at one endpoint. Compare fetching, caching, errors and the N+1 problem.
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SQL vs NoSQL Databases: Differences and How to Choose
Relational schemas, joins and transactions versus document, key-value, wide-column and graph stores, with a SQLite demo and a design exercise.
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A/B Test Sample Size and the Peeking Problem: Interview Guide
Size an A/B test from baseline, MDE, alpha and power, turn it into days, and see by simulation why stopping at the first p below 0.05 fails.
~8 min readread →
Bayes' Theorem and the Base Rate Fallacy: Interview Guide
Solve the classic 1% disease test question three ways, see why rare events wreck precision, and avoid the base rate traps interviewers set.
~8 min readread →
Central Limit Theorem Explained: Data Science Interview Guide
What the central limit theorem really promises, shown by simulation on skewed revenue data, and where it quietly breaks in A/B tests.
~9 min readread →
Confidence Intervals Explained: Data Science Interview Guide
What 95% confidence really means, how to build t, Wilson and bootstrap intervals in Python, and why the textbook proportion interval fails.
~8 min readread →
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