# system-design

#system design#authentication#jwt

API Rate Limiting at Scale: Redis-Based Strategies

API Rate Limiting at Scale with Redis Rate limiting is essential for protecting your APIs from abuse, ensuring fair usage, and preventing cascading failures. Redis is the ideal store for rate limiting because of its spee…

#redis#api-gateway#rate-limiting

DatabasesAdvanced

Database Sharding Part 3: The Shard Key Blueprint

Part 3: The Shard Key Blueprint If you choose the wrong shard key, you will end up with a "Hot Shard"—one server at 100% CPU while the others are at 5%. 1. High Cardinality Choose a key with many unique values (like ). A…

Apr 20, 20261 min read

PlaybookDatabase Sharding Mastery

#database-scaling#shard-key#system-design

Distributed Transactions Part 7: Case Study - The Global Fintech Ledger

Part 7: Case Study - The Global Fintech Ledger This final part brings the full series together using a realistic fintech ledger architecture. The business requirement sounds simple: never lose money, never create money,…

Case StudyDistributed Transactions Mastery

#case-study#ledger#fintech

Graceful Degradation: Feature Shedding

Graceful Degradation Most distributed systems do not fail all at once. They degrade in layers: rising tail latency, thread pool saturation, cache misses, partial dependency outages, then total user-visible failure. Grace…

Apr 20, 20264 min read

#reliability#system-design#resilience

MessagingAdvanced

Retry Queues vs. DLQ: Architecting Resilient Message Consumers

Retry Queues vs. DLQ: Beyond Simple Retries In a high-scale messaging system, failures are not a matter of 'if', but 'when'. Most developers make the mistake of either retrying indefinitely (blocking the partition) or dr…

Apr 20, 20261 min read

Comparison

#kafka#messaging#resilience

Speculative Retries: The Google Approach to Solving Tail Latency

Speculative Retries: Solving the P99 Tail In a large distributed system, the "tail latency" (P99.9) is often dominated by a single "slow" node. This is the Tail at Scale problem. No matter how much you optimize your code…

Deep DiveDistributed Systems Mastery

#system-design#low-latency#p99

System Design: Designing an Ad Click Aggregator

System Design: Designing an Ad Click Aggregator Ad click aggregation is a massive scale data problem. When billions of users click on ads across the web, those clicks must be aggregated, deduplicated, and stored for both…

#system-design#ad-aggregator#analytics

System Design: Designing Airbnb (Hotel/Home Booking)

System Design: Designing Airbnb (Hotel/Home Booking) Designing a platform like Airbnb or Booking.com involves two distinct technical challenges: Search (helping users find the perfect place) and Concurrency (ensuring tha…

#system-design#airbnb#booking-system

System Design: Designing a Collaborative Editor (Google Docs)

System Design: Designing a Collaborative Editor (Google Docs) Designing a collaborative editor like Google Docs or Notion is one of the most technically challenging system design problems. It requires synchronizing the s…

#system-design#google-docs#collaborative-editing

System Design: Designing a Content Delivery Network (CDN)

System Design: Designing a Content Delivery Network (CDN) A CDN is a geographically distributed group of servers that work together to provide fast delivery of internet content. By caching assets (images, videos, JS/CSS)…

#system-design#cdn#caching

System Design: Designing a Content Moderation System (Meta/TikTok Scale)

System Design: Designing a Content Moderation System With billions of users uploading content every minute, platforms like Meta, YouTube, and TikTok must identify and remove harmful content (hate speech, violence, misinf…

#system-design#content-moderation#machine-learning

System Design: Data Partitioning and Sharding Strategies

System Design: Data Partitioning and Sharding When your database outgrows a single machine, you have two choices: Scale Up (bigger machine) or Scale Out (multiple machines). Sharding (Horizontal Partitioning) is the art…

#system-design#sharding#partitioning

System Design: Designing a Database Proxy for Sharding (Vitess Style)

System Design: Designing a Database Proxy for Sharding Scaling a relational database like MySQL or PostgreSQL is one of the hardest challenges in engineering. When a single database server can't handle the load, you must…

#system-design#database-proxy#vitess

System Design: Designing a Digital Wallet and Ledger System

System Design: Designing a Digital Wallet and Ledger System Designing a digital wallet (like PayPal, Venmo, or AliPay) is a masterclass in data integrity. In fintech, "eventual consistency" is often not enough. You need…

#system-design#digital-wallet#ledger

System Design: Designing a Distributed BLOB Store (like S3/GCS)

System Design: Designing a Distributed BLOB Store An object store (BLOB store) is a fundamental building block of cloud infrastructure. Unlike a file system, it provides a simple interface (PUT, GET, DELETE) to store lar…

#system-design#object-storage#distributed-systems

System Design: Designing a Distributed File Lock (Zookeeper/Curator)

Designing a Distributed File Lock In a distributed environment, two instances of a service might try to modify the same shared file at the same time, leading to data corruption. While we have locks for databases (Redis/P…

#system-design#distributed-locking#zookeeper

System Design: Designing a Distributed File System (HDFS/GCS Style)

System Design: Designing a Distributed File System (HDFS) A Distributed File System (like HDFS or GFS) is designed to store massive datasets across a cluster of commodity servers. It handles the complexity of breaking la…

#system-design#hdfs#distributed-storage

System Design: Designing a Distributed ID Generator (Snowflake)

Designing a Distributed ID Generator > Prerequisite: To understand why distributed IDs are hard, first read about Database Sharding and Partitioning. In a distributed system, you often need to generate unique identifiers…

#system-design#snowflake#distributed-id

System Design: Designing a Local-First Key-Value Store (LevelDB/RocksDB)

System Design: Designing a Local-First Key-Value Store While distributed systems get all the glory, the foundation of every database is an efficient local storage engine. Whether it's LevelDB (Google), RocksDB (Meta), or…

#system-design#leveldb#rocksdb

System Design: Designing a Distributed Lock Manager

System Design: Designing a Distributed Lock Manager (DLM) In a microservices architecture, multiple instances of a service often need to access a shared resource (like an inventory item or a single-use coupon) simultaneo…

#system-design#distributed-locking#redis

System Design: Designing a Distributed Lock Service

Designing a Distributed Lock Service Distributed locking is one of the most critical and complex infrastructure components. It provides a "global" synchronization mechanism that ensures resources (like file systems, data…

#system-design#distributed-locking#consistency

System Design: Designing a Distributed Logging System (TB/Day Scale)

System Design: Designing a Distributed Logging System In a microservices architecture with thousands of containers, logs are scattered everywhere. You need a centralized system that can ingest terabytes of log data every…

#system-design#logging#elk-stack

System Design: Designing a Distributed Message Queue (Kafka Architecture)

System Design: Designing a Distributed Message Queue A Distributed Message Queue is the backbone of modern asynchronous architecture. It allows services to communicate without being tightly coupled. While many use Apache…

#system-design#kafka#message-queue

System Design: Designing a Global Distributed Rate Limiter

System Design: Designing a Global Distributed Rate Limiter In a distributed system, a single user or bot can easily overwhelm your backend. A Rate Limiter is your first line of defense. Designing one that is accurate, lo…

#system-design#rate-limiting#redis

System Design: Designing a Distributed Search Engine (Elasticsearch)

System Design: Designing a Distributed Search Engine Search is the most common way humans interact with massive datasets. Building a system that can perform full-text search across billions of documents with millisecond…

#system-design#search-engine#elasticsearch

System Design: Designing a Distributed Task Scheduler

System Design: Designing a Distributed Job Scheduler A Distributed Job Scheduler (like Airflow, Celery, or a custom system) manages the execution of tasks at specific times or intervals. While a simple job works for one…

#system-design#task-scheduler#cron

System Design: Distributed Transactions (2PC and 3PC)

Distributed Transactions: 2PC and 3PC Achieving ACID guarantees across multiple independent databases is the "Holy Grail" of distributed systems. While Sagas are popular for microservices, the classic protocols Two-Phase…

#system-design#distributed-transactions#2pc

System Design: Managing Distributed Transactions with the Saga Pattern

System Design: Managing Distributed Transactions with the Saga Pattern In a monolithic architecture, a single database transaction guarantees ACID properties across all operations. In a microservices architecture, a sing…

#system-design#microservices#saga-pattern

System Design: Designing an E-commerce Checkout System

System Design: Designing an E-commerce Checkout System An e-commerce checkout system is the most critical part of any retail platform. It must handle high concurrency during flash sales, ensure that inventory is never ov…

#system-design#ecommerce#payment-gateway

System Design: Designing a Food Delivery App (Uber Eats / DoorDash)

System Design: Designing a Food Delivery App A food delivery platform (like Uber Eats, DoorDash, or Grab) is more than just an e-commerce site. It is a Three-Sided Marketplace that must coordinate between Customers, Rest…

#system-design#food-delivery#marketplace

System Design: Designing a Real-time Gaming Leaderboard (Massive Scale)

System Design: Designing a Real-time Gaming Leaderboard A leaderboard is a core feature in competitive gaming and fitness apps. While a simple SQL ORDER BY works for 100 users, doing it for 100 million users with real-ti…

#system-design#gaming#leaderboard

System Design: Designing Google Drive (Distributed File Storage)

System Design: Designing Google Drive Designing a distributed file storage system like Google Drive or Dropbox requires more than just uploading files to S3. You must handle large files efficiently, synchronize state acr…

#system-design#google-drive#distributed-storage

System Design: Designing Google Maps (Navigation and ETA)

System Design: Designing Google Maps Designing a navigation system like Google Maps or Waze involves managing massive amounts of geographic data and performing complex graph calculations (Pathfinding) in real-time. 1. Co…

#system-design#google-maps#geospatial

System Design: Designing a Scalable GraphQL API Gateway

Designing a Scalable GraphQL API Gateway GraphQL is popular because it allows clients to request exactly what they need. But when you have 50+ microservices, you cannot have 50 different GraphQL endpoints. You need a Gra…

#system-design#graphql#api-gateway

System Design: Designing a Distributed ID Generation Service

Designing a Distributed ID Generation Service In a microservices world, primary keys must be unique across all shards and databases. Relying on an auto-incrementing database column is not an option as it creates a centra…

#system-design#id-generation#snowflake

System Design: Designing Idempotent APIs for Reliable Services

System Design: Designing Idempotent APIs In a distributed system, network failures are inevitable. A common failure scenario is: "The client sends a request -> The server processes it -> The server's response fails to re…

#system-design#api-design#idempotency

System Design: Designing Instagram (Photo Sharing at Scale)

System Design: Designing Instagram (Photo Sharing at Scale) Instagram is a massive photo-sharing platform where users can follow others, post photos, and view a personalized feed. The core challenges are efficiently stor…

#system-design#instagram#photo-sharing

System Design: Designing a Metrics Monitoring and Alerting System

System Design: Designing a Metrics Monitoring System Monitoring is the nervous system of any production infrastructure. A metrics monitoring system must ingest millions of data points every second, store them efficiently…

#system-design#monitoring#prometheus

System Design: Multi-Leader Database Replication

System Design: Multi-Leader Replication In a single-leader setup, all writes go to one node. This is a bottleneck for global applications. Multi-Leader Replication allows writes to happen at multiple data centers simulta…

#system-design#multi-leader#replication

System Design: Designing Multi-Region Active-Active Architectures

Multi-Region Active-Active: The Global Scale Deploying to multiple regions is the only way to survive a total regional failure and provide sub-100ms latency to a global user base. An Active-Active setup means every regio…

Case StudyReliability Engineering Mastery

#system-design#multi-region#active-active

System Design: Designing Nearby Friends (Real-time Geospatial Streams)

System Design: Designing Nearby Friends (Real-time Geospatial) Designing a "Nearby Friends" feature (like Snapchat's Snap Map or Facebook's Nearby Friends) is a unique challenge. Unlike Yelp or Uber, where the entities (…

#system-design#geospatial#real-time

System Design: Designing an Object Store (Amazon S3 Internals)

System Design: Designing an Object Store (Amazon S3) An Object Store is a distributed storage system designed to store massive amounts of unstructured data (Photos, Videos, Backups). Unlike a file system, it provides a s…

#system-design#s3#object-store

System Design: Designing an Online Auction System (eBay Scale)

System Design: Designing an Online Auction System Designing a high-scale auction system like eBay or a penny auction site is a classic concurrency challenge. The system must handle thousands of users bidding on the same…

#system-design#auction-system#ebay

System Design: Designing an Online Judge (LeetCode/HackerRank)

System Design: Designing an Online Judge An Online Judge system like LeetCode, Codeforces, or HackerRank allows users to submit code, which is then executed and verified against hidden test cases. The core technical chal…

#system-design#online-judge#leetcode

System Design: Designing a Global Payment Gateway (Stripe Scale)

System Design: Designing a Global Payment Gateway A Payment Gateway (like Stripe, PayPal, or Adyen) is the bridge between a merchant's website and the complex world of banks and card networks. It must be 100% reliable, e…

#system-design#fintech#payment-gateway

System Design: Designing a Proximity Service (Yelp/Google Maps)

System Design: Designing a Proximity Service (Yelp) A Proximity Service allows users to find nearby places (restaurants, gas stations, etc.). The technical challenge is searching millions of businesses based on a user's…

#system-design#proximity-service#geohash

System Design: Designing an Event Mesh (Pub/Sub at Global Scale)

System Design: Designing an Event Mesh An Event Mesh is a modern evolution of Pub/Sub. While Pub/Sub manages a single topic, an Event Mesh dynamically routes events between different clouds, data centers, and on-premise…

#system-design#event-mesh#pubsub

System Design: Designing a Pub/Sub Messaging Platform

System Design: Designing a Pub/Sub Messaging Platform A Pub/Sub (Publish/Subscribe) system is a fundamental pattern for decoupling services. It allows producers to send messages without knowing who the consumers are, ena…

#system-design#pubsub#messaging

System Design: Designing a Real-Time Analytics Dashboard

System Design: Designing a Real-Time Analytics Dashboard Real-time analytics dashboards (used for tracking game players, ad clicks, or server metrics) require capturing and visualizing massive data streams. The challenge…

#system-design#analytics#real-time

System Design: Designing a Real-time Bidding (RTB) Ad System

System Design: Designing a Real-time Bidding (RTB) Ad System Real-time Bidding (RTB) is the backbone of the modern digital advertising industry. When you load a webpage, an auction happens in the background to decide whi…

#system-design#rtb#ad-tech

System Design: Designing a Real-time Recommendation Engine (TikTok / Netflix)

System Design: Designing a Real-time Recommendation Engine A recommendation engine is the "secret sauce" behind platforms like TikTok, Netflix, and Amazon. Its goal is to predict what a user will like next based on their…

#system-design#recommendation-engine#ai

The Shadow Database Pattern

The Shadow Database Pattern Schema changes on large production databases are dangerous because rollback is hard, verification is incomplete, and hidden query/path assumptions surface only under real traffic. The Shadow D…

Apr 20, 20264 min read

#system design#database#migration

DatabasesAdvanced

SQL vs NoSQL: Which One for Your Next Production MVP?

SQL vs NoSQL: Making the Right Choice One of the most debated topics in software engineering is whether to use a Relational (SQL) or Non-Relational (NoSQL) database. As a senior engineer, your choice shouldn't be based o…

ComparisonBackend Systems Mastery

#sql#nosql#databases

System Design: Designing a Stock Trading Platform and Matching Engine

System Design: Designing a High-Performance Trading Platform Designing a stock or crypto trading platform is the ultimate test of low-latency engineering. You need to process millions of orders per second, maintain a per…

#system-design#fintech#matching-engine

Project Case Study: Designing Stripe’s Ledger System

Project Case Study: Designing Stripe’s Ledger System Recording transactions between millions of accounts is not a matter of simple arithmetic. It requires a system that is 100% auditable, ACID-compliant, and perfectly co…

#system-design#ledger#fintech

System Design: Designing Ticketmaster (High-Concurrency Booking)

System Design: Designing Ticketmaster The primary challenge of a system like Ticketmaster or Booking.com is not storage, but Concurrency. How do you ensure that when 100,000 users try to book the same 10 front-row seats,…

#system-design#ticketmaster#concurrency

System Design: Designing a URL Shortener (TinyURL)

System Design: Designing a URL Shortener (TinyURL) Designing a URL shortener like TinyURL or Bitly seems simple on the surface, but it's a fantastic exercise in thinking about data encoding, unique ID generation, and hig…

Case StudyBackend Systems Mastery

#system-design#tinyurl#url-shortener

System Design: Solving the Top K Problem (Heavy Hitters)

System Design: Solving the Top K Problem The "Top K" problem (or Heavy Hitters) is about finding the $ most frequent items in a massive stream of data. For example: - YouTube: The top 10 trending videos in the last hour.…

#system-design#top-k#heavy-hitters

System Design: Designing Twitter (Timeline and News Feed)

System Design: Designing Twitter (Timeline and News Feed) Twitter (now X) is a massive real-time messaging system. The core technical challenge is not storing the tweets, but delivering them to millions of followers' tim…

#system-design#twitter#scalability

System Design: Designing Uber (Ride-sharing at Scale)

System Design: Designing Uber (Ride-sharing at Scale) Designing a ride-sharing service like Uber is one of the most popular system design challenges. It requires handling high-frequency location updates, real-time supply…

#system-design#uber#geospatial

System Design: Designing a Web Crawler at Google Scale

System Design: Designing a Web Crawler A Web Crawler (or spider) is an automated system that browses the World Wide Web in a methodical, automated manner to index content for search engines like Google or Bing. 1. Core R…

#system-design#web-crawler#search-engine

System Design: Designing WhatsApp (Real-time Messaging)

System Design: Designing WhatsApp (Real-time Messaging) Building a chat application like WhatsApp or Facebook Messenger requires managing millions of persistent connections and ensuring that messages are delivered reliab…

#system-design#whatsapp#real-time-chat

Project Case Study: Designing YouTube (Video Streaming at Global Scale)

Project Case Study: Designing YouTube YouTube is one of the world's largest distributed systems, managing exabytes of data and serving billions of concurrent users. The technical challenge isn't just "storing a video"—it…

Apr 20, 20265 min read

#system-design#youtube#video-streaming

System Design: Designing a Video Conferencing System (Zoom / MS Teams)

System Design: Designing a Video Conferencing System Designing a real-time video conferencing system like Zoom or Microsoft Teams is fundamentally different from a video streaming service like YouTube. While YouTube prio…

#system-design#webrtc#video-conferencing

What is Load Balancing? A Simple Guide for Backend Engineers

What is Load Balancing? Load balancing is a core component of any distributed system. It acts as a traffic cop sitting in front of your servers and routing client requests across all servers capable of fulfilling those r…

#system design#load balancing#scalability

System Design: Building a Distributed Tracing Platform

Metrics tell you that latency is bad. Logs tell you that something failed somewhere. Traces tell you which request went where, in what order, and where the time actually disappeared. That is why tracing becomes essential…

Apr 18, 202611 min read

#system design#distributed tracing#observability

System Design: Building a Service Discovery Platform

In a distributed system, naming a service is easy. Finding a healthy instance of that service, right now, in the right zone, during a deployment, while failures are happening, is the real problem. That problem is service…

Apr 18, 202610 min read

#system design#service discovery#microservices

System Design: Building a Session Management Platform

Sessions feel simple until they become a security boundary. A user logs in. The system gives them a token or cookie. Requests work. End of story. Then reality arrives: - one user is logged in on five devices - an access…

Apr 18, 202611 min read

#system design#session management#authentication

System Design: Building a Workflow Orchestration Platform

Many backend processes start life as a queue consumer and a couple of retries. That works until the business process gets longer and stranger. Now the flow needs: - wait for payment confirmation - call three downstream s…

Apr 18, 202612 min read

#system design#workflow orchestration#distributed systems

System Design: Building a Distributed Cache

At small scale, cache looks like a simple optimization. Put Redis in front of the database, cache a few expensive reads, and enjoy lower latency. At production scale, a distributed cache stops being a helper library and…

Apr 10, 202614 min read

#system design#distributed cache#redis

System Design: Building a Distributed Configuration Platform

Most systems begin with configuration as a file. That works for a while. Then one service needs a database URL rotation without redeploy. Another wants per-environment rate limits. A third wants tenant-specific limits. A…

Apr 10, 202611 min read

#system design#configuration#distributed systems

System Design: Building a Fraud Detection Platform

Fraud detection is not a single model. It is a decision system that has to operate under latency pressure, incomplete information, adversarial behavior, and messy business trade-offs. If the system is too loose, fraud lo…

Apr 10, 202613 min read

#system design#fraud detection#payments

System Design: Building an Inventory Reservation System

Inventory looks easy until traffic spikes. A product has 10 units. Ten customers should be able to buy it. The eleventh should not. In practice, that clean rule gets blurred by carts, payment retries, partial failures, s…

Apr 10, 202616 min read

#system design#inventory#ecommerce

System Design: Building a Payment Reconciliation Engine

Payments look simple from the product surface. A customer pays. The UI says success. The order moves forward. Under the hood, though, the money and the system state do not move in a single atomic transaction. A payment g…

Apr 10, 202616 min read

#system design#payments#reconciliation

System Design: Building a Search Indexing Platform

Search gets demoed as a search box. Search gets operated as a distributed data synchronization problem. The hard part is usually not querying Elasticsearch or OpenSearch. The hard part is getting the right data into the…

Apr 10, 202611 min read

#system design#search#elasticsearch

System Design: Building an API Gateway Platform

An API gateway is the front door to your backend. It receives traffic before your services do, which makes it powerful and dangerous. A good gateway centralizes routing, authentication, rate limiting, request shaping, ob…

Apr 8, 20268 min read

#system design#api gateway#rate limiting

System Design: Building an Authorization Service

Authentication answers "Who are you?" Authorization answers "What are you allowed to do?" Most systems start with a simple role column on the user table. That works until the product grows. Then permissions become tenant…

Apr 8, 202613 min read

#system design#authorization#permissions

System Design: Building a Data Export Platform

Data export is one of those features that sounds small until it takes down production. A product manager asks for "Export to CSV." The first implementation runs a SQL query in the web request, builds a file in memory, an…

Apr 8, 202611 min read

#system design#data export#async jobs

System Design: Building an Email Delivery Platform

Sending one email is easy. Sending millions of emails reliably, legally, and without damaging your domain reputation is a system design problem. Email delivery touches product workflows, background jobs, third-party prov…

Apr 8, 202610 min read

#system design#email delivery#queues

System Design: Building a Feature Flag Platform

A feature flag platform decouples deployment from release. Code can be deployed safely while the feature remains disabled, then enabled gradually for internal users, beta customers, 1% of traffic, 10% of traffic, and eve…

Apr 8, 20269 min read

#system design#feature flags#progressive delivery

System Design: Building a File Upload Platform

File upload looks easy until production traffic arrives. Users upload huge files, mobile networks drop halfway through, browsers retry, malicious files appear, thumbnails fail, metadata gets out of sync, signed URLs expi…

Apr 8, 202610 min read

#system design#file upload#object storage

System Design: Building a Distributed Job Scheduler

A job scheduler sounds simple: run this task at this time. In production, that becomes a distributed systems problem. Nodes crash after claiming work. Clocks drift. Jobs overlap. Cron expressions are ambiguous. Tenants n…

Apr 8, 202611 min read

#system design#job scheduler#distributed systems

System Design: Building a Metrics Platform Like Prometheus

Metrics platforms answer operational questions quickly: - Is error rate increasing? - Which service owns the latency spike? - Did a deployment change request volume? - Which tenant is causing the queue backlog? - Are we…

Apr 8, 202610 min read

#system design#metrics#observability

System Design: Building a Secrets Management Platform

Secrets management looks like a simple storage problem until you operate it in production. At first, the requirement sounds like this: "Store API keys and database passwords somewhere safe." Then real systems arrive. Ser…

Apr 8, 202613 min read

#system design#secrets management#security

System Design: Building a Usage Metering and Billing Platform

Usage-based billing looks straightforward: count what the customer used and charge them for it. In production, it becomes one of the most sensitive systems in the company. If usage is undercounted, you lose revenue. If i…

Apr 8, 20269 min read

#system design#billing#usage metering

System Design: Building a Webhook Delivery Platform

Webhooks look simple from the outside: "When something happens, send an HTTP POST to the customer's URL." In production, that sentence becomes a distributed delivery system. Customers have slow endpoints, invalid TLS cer…

Apr 8, 202611 min read

#system design#webhooks#event driven architecture

Multi-Region Architecture: Active-Active, Active-Passive, and Consistency Trade-Offs

Multi-region architecture is expensive insurance. It can improve availability and latency, but it also makes data consistency, deployment, observability, and operations much harder. Before designing multi-region, ask two…

Apr 7, 20265 min read

#multi-region#system design#distributed systems

System Design: Building an Audit Log System for Compliance and Debugging

Audit logs answer a simple question: who did what, to which resource, from where, and when? That question matters during security investigations, customer support, compliance audits, data recovery, and debugging. A norma…

Apr 7, 20265 min read

#system design#audit logs#compliance

AI/MLAdvanced

System Design: Building a Feature Store for Real-Time Machine Learning

Production machine learning systems fail when the model sees different data in training than it sees in production. A feature store helps solve that problem. It provides a consistent way to define, compute, store, and se…

Apr 7, 20265 min read

#feature store#machine learning#system design

System DesignExpert

Event Sourcing and CQRS in Production: Beyond the Theory

Event sourcing is one of those patterns that looks elegant in conference talks and becomes surprisingly complex in production systems. The theory — store events instead of state, derive state by replaying events — is sou…

Jun 23, 20257 min read

#event sourcing#cqrs#system design

System DesignExpert

gRPC vs REST vs GraphQL: Choosing the Right API Protocol

API protocol selection has a longer lifespan than almost any other technical decision. REST APIs from 2010 are still running in production. gRPC services chosen for internal communication in 2018 are tightly coupled to t…

Jun 18, 20257 min read

Comparison

#grpc#rest#graphql

Multi-Tenancy Architecture: Database, Application, and Infrastructure Patterns

Multi-tenancy is the architecture pattern where a single deployed instance of a software system serves multiple customers (tenants), with each tenant's data logically or physically isolated from others. It's the foundati…

May 24, 20258 min read

#multi-tenancy#saas#system design

Feature Flags and Progressive Delivery: Safe Releases at Scale

Feature flags — also called feature toggles or feature switches — decouple code deployment from feature release. You deploy code to production with the new feature disabled. When you're ready, you enable it for 1% of use…

May 19, 20257 min read

#feature flags#progressive delivery#deployment

Microservices Are Overrated for Most Startups

The microservices hype peaked around 2016. In 2025, some of the most respected engineering teams in the industry are quietly talking about their microservices regret. Segment famously consolidated 130+ microservices back…

May 16, 20259 min read

#microservices#monolith#architecture

Designing a High-Throughput Notification System for 100K Events per Second

100,000 events per second is not a notification system problem — it's a data pipeline problem that happens to produce notifications. Teams that approach it as a features problem ("we just need push, email, and SMS") buil…

May 10, 202510 min read

#system design#notifications#kafka

WebSocket and SSE for Real-Time Systems: Architecture and Production Patterns

Real-time features — live notifications, collaborative editing, live dashboards, streaming data — require pushing data from server to client without the client repeatedly polling. HTTP polling wastes resources and adds l…

May 4, 20257 min read

#websocket#sse#real-time

Designing Idempotent Payment Systems in Distributed Architecture

Duplicate payments are not a theoretical edge case. In any distributed payment system operating at scale, they are a guaranteed occurrence. Networks time out. Clients retry. Proxies retry on behalf of clients. Load balan…

Apr 26, 202511 min read

#payments#idempotency#distributed systems

DatabasesAdvanced

Designing a Database Sharding Strategy for 100 Million Users

Vertical scaling has a ceiling. For most applications, that ceiling arrives somewhere between 1 million and 10 million users, depending on write patterns and data size. At 100 million users, the question is not whether t…

Apr 14, 20259 min read

Case StudyBackend Systems Mastery

#databases#sharding#postgresql

System Design: Video Streaming Platform at Netflix Scale

Netflix accounts for 15% of global internet traffic. At peak, it serves 250 million concurrent streams — each stream adapting in real-time to network conditions, each segment served from servers 20ms away from the viewer…

Mar 19, 202511 min read

#system design#video streaming#cdn

System Design: Real-Time Chat Application at Scale

Real-time chat systems are among the most architecturally interesting distributed systems. They require persistent connections at massive scale, exactly-once message delivery guarantees, presence detection across million…

Mar 17, 202511 min read

#system design#websocket#real-time

API Design: REST vs GraphQL vs gRPC — When to Use Each

Every microservices architecture makes an implicit bet on an API protocol. REST is familiar but verbose. GraphQL is flexible but complex. gRPC is fast but opinionated. Choosing wrong costs you months of refactoring. This…

Mar 1, 202513 min read

Comparison

#api#rest#graphql

System Design: Search Autocomplete at Google Scale

Search autocomplete — the dropdown that appears as you type — seems simple but is one of the most latency-sensitive features in any product. Google returns suggestions in under 100ms for billions of queries per day. This…

Feb 20, 202511 min read

#system design#search#autocomplete

System Design: Building a Notification System for 100 Million Users

Notification systems are deceptively complex. Sending one notification is trivial. Sending 100 million notifications daily — with channel routing, user preferences, delivery tracking, retry logic, and rate limiting — req…

Feb 18, 202511 min read