FreeBytes Blog
In-depth guides on financial planning, tax calculations, and tech interview preparation — written to explain the why, not just the what.
How to Design a URL Shortener — System Design Interview
Step-by-step system design for a URL shortener like bit.ly. Covers base62 encoding, redirect flow, caching strategy, analytics pipeline, and scaling to billions of URLs.
How to Design a Rate Limiter — System Design Interview
Design a distributed rate limiter from scratch. Compare fixed window, sliding window, token bucket, and leaky bucket algorithms with Redis-based implementation.
How to Design a Notification System — System Design Interview
Design push, SMS, and email notifications at scale. Covers fan-out architecture, priority queues, retry logic, deduplication, and user preference management.
How to Design a Chat System — System Design Interview
Design a real-time chat app like WhatsApp. WebSockets, message storage, group chat fan-out, presence detection, delivery receipts, and media storage at scale.
How to Design a News Feed — System Design Interview
Design Facebook/Twitter-style news feed. Fan-out on write vs fan-out on read, celebrity problem, Redis sorted sets for feed storage, and cursor-based pagination.
How to Design a File Storage System like Dropbox
Design a cloud file storage system. Block chunking, content-addressable deduplication, delta sync, metadata vs file store separation, versioning, and conflict resolution.
How to Design Search Autocomplete — System Design Interview
Design a typeahead search system. Trie data structure, top-K suggestions, distributed trie sharding, query frequency scoring, and sub-100ms latency requirements.
How to Design a Distributed Cache System
Design a distributed cache from scratch. Cache-aside vs write-through vs write-back, eviction policies, cache stampede prevention, consistent hashing, and Redis cluster.
How to Design a Payment System — System Design Interview
Design a payment system like Stripe. Idempotency keys, double-entry bookkeeping, PSP integration, webhook delivery, reconciliation jobs, and PCI DSS compliance.
What is Consistent Hashing — System Design Explained
Consistent hashing solves the problem of remapping all keys when a cache/DB node is added or removed. Learn virtual nodes, the hash ring, and how Redis Cluster and Cassandra use it.
What is a Bloom Filter — Probabilistic Data Structures Explained
A Bloom filter tests set membership in O(1) time with zero false negatives. Learn the bit array + hash function mechanics, false positive rate formula, and real-world use in Cassandra and Chrome.
What is LRU Cache — How It Works and How to Implement It
LRU (Least Recently Used) evicts the least-recently accessed item when the cache is full. Learn the HashMap + doubly linked list implementation for O(1) get/put, and when to use LFU instead.
Write-Through vs Write-Back vs Cache-Aside — Caching Strategies
Three cache write strategies compared: cache-aside (app manages cache), write-through (write to cache and DB together), write-back (write cache first, async to DB). Includes when to use each.
What is Thundering Herd Problem — and How to Fix It
Thundering herd happens when a hot cache key expires and thousands of requests simultaneously slam the database. Learn mutex locks, probabilistic early expiry, staggered TTLs, and request coalescing.
What is an Idempotent API — Idempotency in REST and Payments
An idempotent operation produces the same result no matter how many times it runs. Learn HTTP method idempotency, idempotency keys for payments, Redis-based implementation, and Stripe's approach.
What is the Saga Pattern — Distributed Transactions Explained
The saga pattern manages distributed transactions across microservices without 2PC. Learn choreography vs orchestration sagas, compensating transactions, and e-commerce order flow examples.
What is the Outbox Pattern — Reliable Event Publishing
The outbox pattern ensures DB writes and message queue publishes stay in sync. Write events to an outbox table in the same transaction, then relay them with CDC (Debezium) or a poller.
What is API Versioning — Strategies and Best Practices
API versioning lets you evolve your API without breaking existing clients. Compare URL versioning, header versioning, and content negotiation — with deprecation strategy and real Stripe/Twilio examples.
What is the Retry Pattern — Exponential Backoff and Jitter
Transient failures in distributed systems need smart retry logic. Learn exponential backoff, jitter to prevent thundering herd, retry budgets, non-retryable errors, and circuit breaker integration.
What is Data Partitioning — Sharding Strategies Explained
Data partitioning (sharding) splits large datasets across multiple database nodes. Compare range-based, hash-based, consistent hashing, and directory-based sharding — with cross-shard query trade-offs.
CAP Theorem Explained — Consistency, Availability & Partition Tolerance
A distributed system can only guarantee 2 of 3: Consistency, Availability, Partition Tolerance. Learn what CAP means in practice and how MongoDB, Cassandra, PostgreSQL, and DynamoDB each make the trade-off.
SQL Joins Explained — INNER, LEFT, RIGHT, FULL OUTER JOIN
Master every SQL JOIN type with visual Venn diagrams, sample data, and real queries. INNER, LEFT, RIGHT, FULL OUTER, CROSS, and SELF joins — with performance tips.
MySQL vs PostgreSQL — Which Database to Choose
Compare MySQL and PostgreSQL on features, JSON support, replication, licensing, and ecosystem. Learn which fits your project — with real-world use case guidance.
What is Apache Kafka and When to Use It
Kafka is a distributed event streaming platform powering real-time data pipelines at Netflix, LinkedIn, and Uber. Learn topics, partitions, consumer groups, and Kafka vs RabbitMQ.
What is Kubernetes and How It Works — K8s Explained
Kubernetes automates deployment, scaling, and management of containers. Learn Pods, Deployments, Services, Ingress, and when to use K8s vs Docker Compose — with YAML examples.
CSR vs SSR vs SSG — Rendering Strategies Explained
Client-Side Rendering, Server-Side Rendering, Static Site Generation, and ISR — each has different performance, SEO, and complexity trade-offs. Learn which to use for SPAs, Next.js, and e-commerce.
React vs Vue vs Angular — Which Framework to Choose in 2026
The three dominant frontend frameworks compared: architecture, learning curve, ecosystem, performance, and job market. Includes a decision guide for picking the right one for your project.
Promise vs Callback vs Async/Await in JavaScript
Learn how JavaScript handles asynchronous code — from callback hell to Promises to async/await. Covers promise chaining, Promise.all, error handling, and the parallel execution pattern.
What is the JavaScript Event Loop — Explained Simply
Why can JavaScript handle async operations if it's single-threaded? The event loop, call stack, task queue, and microtask queue explained with visualisations and code examples.
var vs let vs const in JavaScript — Complete Guide
Scope, hoisting, Temporal Dead Zone, reassignment — everything you need to know about JavaScript variable declarations with clear code examples and the modern convention.
Horizontal vs Vertical Scaling Explained
Scale up vs scale out — the core decision in system design. Covers stateless architecture, load balancers, database scaling, auto-scaling, and real examples from Instagram and Twitter.
Microservices vs Monolith — Architecture Comparison
When do microservices make sense and when are they overkill? Real trade-offs, common pitfalls (distributed monolith), and how Netflix, Amazon, and Shopify approached the decision.
SOLID Principles Explained with Examples
The five object-oriented design principles that make code maintainable and testable — SRP, OCP, LSP, ISP, DIP — each explained with a bad code example, good code example, and the benefit.
OOP Concepts Explained — Classes, Objects, Inheritance & More
Object-Oriented Programming explained with clear code examples. The four pillars (encapsulation, inheritance, polymorphism, abstraction), class vs object, and OOP vs functional programming.
What is Database Indexing and Why It Matters
Indexes are the single most impactful query optimisation. Learn B-tree indexes, composite indexes, the left-prefix rule, clustered vs non-clustered, and when (not) to add an index.
What is Redis and When to Use It — Complete Guide
Redis stores data in RAM for microsecond-fast access. Learn its data structures (strings, hashes, sorted sets, streams), caching, rate limiting, pub/sub, leaderboards, and Redis vs Memcached.
What is an API Gateway — How It Works and When to Use One
An API gateway is the single entry point for all microservice calls — handling routing, auth, rate limiting, SSL termination, and request transformation. Learn how it compares to a reverse proxy.
What is a CDN and How It Works — Content Delivery Network Explained
CDNs serve assets from edge servers close to users — cutting latency, absorbing traffic spikes, and providing DDoS protection. Covers cache invalidation, Cache-Control headers, and CDN providers.
TCP vs UDP — Key Differences Explained
TCP guarantees delivery and order; UDP is fast and connectionless. Learn why DNS uses UDP, why video calls use UDP, what QUIC is, and when to choose each protocol.
HTTP Status Codes Explained — 200, 301, 404, 500 and More
Complete reference for every HTTP status code class: 2xx success, 3xx redirects, 4xx client errors, 5xx server errors. Includes 401 vs 403, 301 vs 302, and REST API design guidance.
How a Browser Works — From URL to Rendered Page
What happens in those 500ms between pressing Enter and seeing a page? DNS lookup, TCP + TLS, HTTP request, HTML parsing, DOM + CSSOM construction, layout, paint, and compositing — the complete pipeline explained.
Big O Notation Explained Simply — Time & Space Complexity
Understand O(1), O(log n), O(n), O(n log n), O(n²) with simple code examples. Learn how to calculate complexity, compare data structure operations, and use Big O in interviews and real code.
SQL vs NoSQL — Key Differences and When to Use Each
SQL enforces schemas and ACID transactions; NoSQL trades structure for scale and flexibility. This guide covers all four NoSQL types, compares them to relational databases, and helps you pick the right tool.
What is CI/CD Pipeline — Continuous Integration & Delivery Explained
CI/CD automates testing and deployment so teams ship faster with confidence. Learn how a pipeline works, the difference between CI, CD and Continuous Deployment, and how to set up GitHub Actions.
What is Docker and How It Works — Containers Explained
Docker packages apps and dependencies into containers that run identically everywhere. Covers images vs containers, Dockerfile, Docker Compose, VM vs container comparison, and essential commands.
What is a REST API — Methods, Status Codes & Best Practices
REST APIs power every modern web and mobile app. Learn HTTP methods, URL design, status codes, the 6 REST constraints, and a REST vs GraphQL vs gRPC comparison — with examples.
What is CORS and How to Fix It — Complete Guide
CORS errors are the most common frontend headache. Learn what Same-Origin Policy is, how preflight requests work, and exactly how to fix CORS in Node/Express, Nginx, and PHP.
How JWT Works — JSON Web Tokens Explained
JWT is the most widely-used token format for API authentication. Learn the 3-part structure, HS256 vs RS256 signing, JWT vs session tradeoffs, secure storage, and common security pitfalls.
How HTTPS Works — SSL/TLS Explained for Developers
HTTPS encrypts web traffic and authenticates servers. This guide explains the TLS handshake, symmetric vs asymmetric encryption, certificate types, TLS 1.2 vs 1.3, and HSTS.
What is DNS and How It Works — Complete Guide
DNS translates domain names to IP addresses. Learn the 7-step resolution process, all DNS record types (A, MX, CNAME, TXT, NS), TTL, public resolvers, and how to debug DNS issues from the command line.
Nginx Configuration Guide — Optimization, Reverse Proxy & Caching
Complete production Nginx guide: performance tuning (worker processes, sendfile, keepalive), gzip/Brotli compression, browser caching, FastCGI cache, reverse proxy setup for Node.js & PHP, SSL/TLS with HTTP/2, load balancing, rate limiting, and security hardening — with copy-ready config examples.
The Power of Compounding — How Small Savings Become a Fortune
Compounding is the quiet engine that turns ordinary savers into wealthy retirees. Learn how frequency and time drive growth, why starting early beats investing more, and how to put compounding to work.
CTC vs In-Hand Salary — Why Your Take-Home Is Lower
Signed for ₹12 lakh but your account credits ₹85,000 a month? This guide breaks down where your money goes, layer by layer — EPF, gratuity, professional tax and income tax — using FY 2025-26 rules.
Old vs New Tax Regime — Which Saves More Tax in 2026?
India now has two income tax regimes running in parallel. The New Regime offers lower slab rates but strips away deductions. This guide compares both with break-even analysis and actual tax calculations for different salary levels.
How Gratuity Is Calculated — Rules, Formula & Eligibility
Gratuity is a retirement benefit your employer must pay after 5+ years. This guide covers the 15/26 formula, rounding rules, tax exemption limits, and worked examples for private sector employees.
What Is CAGR and Why It Matters for Your Investments
CAGR cuts through the noise of volatile returns and gives you one clean annualised number. Learn the formula, why it beats average returns, and how to use it for comparing investments across asset classes.
PPF vs FD vs SSY — Best Safe Investment in India 2026
Compare returns, tax treatment, lock-in periods, and liquidity of India's three safest investment options. Includes post-tax return calculations and a smart allocation strategy.
Stamp Duty in India — State-wise Rates & How to Save
Stamp duty adds 5-10% to your property cost. This guide covers state-wise rates for 2026, how it's calculated, women buyer concessions, and legal strategies to reduce your registration expenses.
401(k) vs IRA — Which Retirement Account Is Better?
Compare contribution limits, employer matching, investment options, and tax treatment of 401(k) and IRA accounts. Includes the optimal contribution strategy and Roth vs Traditional decision framework.
How Mortgage Amortization Works — With Examples & Schedule
Understand why early mortgage payments are mostly interest, how extra payments save thousands, the 15-year vs 30-year trade-off, and when refinancing makes sense — with full amortization tables.
How to Calculate HRA Exemption in 2025 — Step by Step
If you live in rented accommodation, you can claim HRA exemption and reduce your taxable income significantly. This guide walks through the exact formula, Metro vs Non-Metro rules, and a worked example with actual numbers.
SIP vs FD — Which Is Better for a 5-Year Goal in 2025?
Both SIP and FD are popular savings instruments in India, but they serve very different purposes. This guide compares returns, risk, liquidity, and tax treatment — with a real number comparison for a ₹5,000/month investment over 5 years.
What is a Closure in JavaScript?
How functions remember their lexical scope, the classic var-in-a-loop bug fixed with let, and real-world uses like private state, memoization, and the module pattern.
ACID Properties in Databases Explained
Atomicity, Consistency, Isolation, Durability — explained with a bank transfer example, the four isolation levels, and how ACID compares to the BASE model used by many NoSQL systems.
Database Normalization: 1NF, 2NF, 3NF Explained
A step-by-step walkthrough of normal forms using one evolving example table, the three anomalies normalization prevents, and when denormalization is the right trade-off instead.
Recursion vs Iteration Explained
How the call stack grows and unwinds during recursion, base case vs recursive case, why naive Fibonacci is exponential, and what tail call optimization actually does.
Thread vs Process: What's the Difference?
Why threads share memory and processes don't, what makes context switching expensive, multithreading vs multiprocessing, and how this plays out in Node.js and Python's GIL.
Hashing vs Encryption vs Encoding
Three commonly confused transformations explained side by side — why passwords should be hashed not encrypted, and why Base64 encoding provides zero security at all.
Mutability vs Immutability Explained
Why React can't detect mutated state, why const doesn't mean immutable, and how libraries like Immer use structural sharing to make immutable updates fast.
Monorepo vs Polyrepo: Which Should You Choose?
Why monorepo doesn't mean monolith, atomic cross-project commits, how Google scales a single repo to billions of lines, and when a polyrepo is the simpler choice.
Circuit Breaker Pattern Explained
The closed, open, and half-open states that stop cascading failures in distributed systems — how it differs from retry, and where it's implemented (Hystrix, resilience4j, Istio).
How EMI Is Calculated — The Formula, the Maths, and What Banks Don't Tell You
EMI looks like a simple monthly payment but the maths behind it is more interesting than most people realise. This guide explains the reducing balance formula, shows the full amortisation logic, and reveals why paying one extra EMI a year can cut your loan by years.