System Design

System Design: Rate Limiting

System Design: Circuit Breaker Pattern - AICassindra

Deep dive into the Circuit Breaker pattern for building resilient distributed systems.

Bloom Filters

Bloom Filters

The Saga Pattern: Managing Distributed Transactions

The Saga Pattern: Managing Distributed Transactions

System Design: Load Balancing - AICassindra

Deep dive into Load Balancing strategies, algorithms, and implementation patterns in distributed systems.

Airbnb Smart Pricing Architecture

The ML system that suggests nightly prices to hosts across millions of listings.

Alipay Super-App Architecture

China's other super-app: mobile payments + credit + wealth management at 1.3B users.

Amazon Shopping Cart Architecture

How Amazon keeps carts consistent across sessions, devices, and unavailable items.

API Gateway Architecture

The gateway pattern: single entry for many services + built-in auth, rate-limit, transform.

API Gateway Patterns

Backend for Frontend, response aggregation, and cross-cutting concerns at the edge.

API Versioning Strategies

How to evolve APIs without breaking existing clients.

ATM End-to-End Architecture

From card insertion to cash dispense: every service, network hop, and reconciliation step.

Autocomplete / Typeahead Architecture

Prefix trees, ranking, and sub-100ms latency for search suggestions.

Bulkhead Pattern

How to prevent one slow service from starving all thread pools.

Cache Aside vs Write-Through vs Write-Behind

The three cache-integration patterns, when each wins, and their consistency tradeoffs.

Cache Invalidation Strategies

TTL, write-through invalidation, versioning, and pub/sub. Trade freshness vs load.

Cache Stampede Prevention

The problem: hot key expires, 1000 concurrent requests slam the DB. Three solutions.

CDN Architecture

How content delivery networks minimize latency by caching close to users.

CDN Cache Hierarchy

Multi-tier caching that turns global content into local responses.

CDN Architecture

How a modern CDN uses anycast + edge compute to serve billions of requests globally.

Circuit Breaker Pattern

The three states + how to configure for your traffic + failure profile.

CQRS + Event Sourcing Architecture

Split writes (commands) from reads (queries), persist events instead of state.

Credit Card Payment Flow Architecture

The complete authorization + capture + settlement flow across acquirer, network, and issuer.

Database Sharding Architecture

How to split a table across N databases, with routing + rebalancing.

Designing a Real-Time Chat System (1M concurrent users)

End-to-end architecture for a WhatsApp-scale chat system, from connection layer to message storage.

Designing an API Gateway

Routing auth rate-limit observability in one tier.

Designing a Distributed Cache (Memcached/Redis-style)

Consistent hashing replication and eviction policies.

Designing an Event-Driven Order System

State machine, idempotency, and the recovery story.

Designing a Feature Flag System

Targeting, rollout, kill switch, and audit.

Designing a File Upload Service (S3-style)

Resumable uploads multipart deduplication and lifecycle policies.

Designing a Metrics Aggregation System

Time-series ingest pre-aggregation and downsampling.

Designing a Notification Service

Push email SMS multi-channel fan-out with retries.

Designing a Payment System

Idempotency keys ledger reconciliation and PCI scope.

Designing a Quota System

Token bucket, sliding window, distributed counters.

Designing Search at Scale

Inverted index, ranking, freshness, personalization.

Designing Search Autocomplete

Trie-based prefix matching with personalization.

Designing Uber Dispatch System

Geo-indexing matchmaking and surge pricing.

Designing a URL Shortener (TinyURL-scale)

Hashing collision strategies database choice and analytics.

Directory-Based Sharding

Explicit key-to-shard mappings for maximum flexibility and per-tenant isolation.

Discord Architecture

How Discord handles millions of concurrent voice channels + huge text servers with low latency.

Distributed Cache Architecture

How a horizontally-scaled cache handles millions of keys across N nodes, with the resharding strategy.

Distributed Cache Consistency Models

Strong vs eventual consistency options for distributed caches, with fault behavior.

DoorDash Architecture

How DoorDash coordinates customers, restaurants, and Dashers with real-time dispatch.

Dropbox File Sync Architecture

How Dropbox syncs files across devices with delta sync + block-level dedup.

Elasticsearch Cluster Architecture

How Elasticsearch distributes an index across nodes with sharding + replication.

Email Delivery Architecture

How email gets from sender to recipient through anti-spam gauntlets.

Event-Driven Microservices Architecture

How services communicate via events instead of synchronous calls, with the failure modes.

Facebook Messenger Architecture

Meta's messenger stack: MySQL-derived TAO + custom binary protocol + optional Signal E2E.

Real-Time Fraud Detection System Architecture

How payment platforms score millions of transactions/second in under 100ms.

Geo-Partitioning

Sharding by geography for compliance + user latency wins.

Google Drive + Docs Real-Time Collaboration Architecture

Operational Transformation and CRDTs behind multi-user document editing.

Google Maps Real-Time Traffic Architecture

How aggregated GPS pings from billions of phones become live traffic overlays.

Google Search Architecture

How Google indexes 100B+ pages and returns relevant results in <200ms.

Grab Architecture

Grab's evolution from ride-hailing to rides + food + payments + more across 8 countries.

GraphQL Architecture

Query language, resolvers, N+1 problem, and DataLoader patterns.

gRPC + Protobuf Architecture

How gRPC delivers 10x smaller payloads and streaming across languages.

Hash Sharding

Hash-based sharding: mechanics, hotspot avoidance, rebalancing tradeoffs.

iCloud Sync Architecture

How Apple keeps notes, photos, contacts, and messages in sync across every Apple device.

Idempotency Key Pattern

How idempotency keys enable safe retries without duplicate charges or double-writes.

iMessage Architecture

How iMessage delivers end-to-end encrypted messages across Apple devices using APNs + cloud sync.

Instagram Feed Generation Architecture

Photo + video feed with ranking, stories, and reels at Facebook-scale infrastructure.

Kafka Partition Architecture

How Kafka's partition model scales throughput and delivers ordered messages within a key.

L4 vs L7 Load Balancer Architecture

Where each operates in the stack, decision points, and when to use which.

LinkedIn Architecture

How LinkedIn serves 1B members with a mix of Kafka, Espresso, and Voldemort at Microsoft-scale infra.

Meta Threads Architecture

How Threads launched in 5 days by leveraging Instagram's infrastructure.

PayPal P2P Architecture

How PayPal processes billions of P2P transfers with balance-based ledger + bank integration.

Range Sharding

Range-based sharding for time-series, geo queries, and ordered scans.

Rate Limiter Architecture

Two canonical rate limiter algorithms, side by side, with an inline architecture diagram.

Rate Limiting Strategies Compared

Token bucket, leaky bucket, fixed window, sliding window — when each one is wrong.

Recommendation System Architecture

Two-tower models, candidate generation, ranking, and serving at 200M+ user scale.

Reddit Architecture

How Reddit ranks 100K+ subreddit posts and comments with the classic hot algorithm.

REST API Design Deep Dive

Resource modeling, verb semantics, versioning, and hypermedia for real REST APIs.

Robinhood Trading Architecture

Zero-commission mobile-first trading and the payment-for-order-flow economics.

Amazon S3 Object Storage Internals

How S3 achieves 11 nines durability + infinite scale via erasure coding + partition placement.

Saga Pattern for Distributed Transactions

Long-running business transactions via compensating steps instead of 2PC.

API gateway architecture

Deep-dive on API gateway design: data plane vs control plane, route matching and filter chains, JWKS-cached auth, distributed rate limiting, retry bud…

Backpressure architecture

Deep-dive on backpressure: reactive signals, bounded queues, shedding, admission control, retry with backoff, fallback, chaos.

Bulkhead pattern architecture

Deep-dive on bulkhead: per-dep thread pool, semaphore, reject, fallback, breaker integration, observability, sizing.

Cache stampede architecture

Deep-dive on cache stampede prevention: singleflight, probabilistic early expiration, TTL jitter, async refresh, circuit breaker.

Content Delivery Network Architecture in Depth

A 2500-word walkthrough of CDN architecture: client, edge PoP, origin shield, origin, cache rules, purge, optimization, TLS, edge compute, analytics, …

Circuit breaker architecture

Deep-dive on circuit breakers: states, failure + slow-call thresholds, half-open probe, fallback, bulkheads, observability.

CQRS architecture

Deep-dive on CQRS (Command Query Responsibility Segregation): splitting the write model that validates commands and mutates a normalized source of tru…

Dead-letter queue architecture

Deep-dive on the dead-letter queue: the delivery counter and retry policy, broker-level vs application-level dead-lettering, the failure-metadata cont…

Distributed lock architecture

Deep-dive on distributed locks: consensus-backed lock services (etcd, ZooKeeper), lease TTLs and sessions, fencing tokens checked at the resource, wai…

Event sourcing architecture

Deep-dive on event sourcing: commands and aggregates that emit events, the append-only event store as source of truth, rehydrating state by replay, sn…

Geo-distributed systems -- serving the world with low latency

Deep-dive on geo-distributed systems: the latency/availability/law drivers, multi-region replicas, data placement, the speed-of-light consistency-vs-l…

Gossip protocol architecture - epidemic membership, failure detection, and anti-entropy

Deep-dive on gossip protocols: the SYN/ACK/ACK2 digest exchange and version merge, phi-accrual failure detection and suspicion lifecycle, anti-entropy…

Hot-key mitigation architecture

Deep-dive on surviving hot keys in sharded systems: why hashing concentrates load, approximate hotspot detection, edge caching for read-hot keys, key …

Idempotency architecture

Deep-dive on idempotency architecture: keys, dedupe store, retry policy, conflict handling, cross-service propagation, TTL, and audit.

Leader election architecture

Deep-dive on leader election: quorum-based campaigning, terms/epochs, leases and heartbeats for bounded failover, fencing tokens that neutralize a sta…

Load shedding -- dropping work to survive overload

Deep-dive on load shedding: the overload-collapse problem, rejecting excess load, serve-some-well-rather-than-all-badly, fail fast (early rejection), …

Notification System Architecture in Depth

A 2500-word walkthrough of a notification system: producers, ingest queue, notification service, preferences, dedup + batching, channels, delivery tra…

Transactional outbox architecture

Deep-dive on the transactional outbox pattern: why commit-then-publish dual writes lose or fabricate events, writing the event to an outbox table in t…

Pub/sub system design architecture

Deep-dive on pub/sub design: topics, partitions, consumers, delivery guarantees, retention, DLQ, schema registry, and metrics.

Distributed Rate Limiter Architecture in Depth

A 2500-word walkthrough of a production distributed rate limiter: edge, gateway, local token bucket, global sliding window, Redis + Lua, fallback, and…

Rate limiting architecture

Deep-dive on rate-limiting architecture: local buckets + shared counters + sliding-window smoothing + policy pipeline for safe changes.

Read-replica routing architecture

Deep-dive on routing reads to replicas safely: read classification, LSN/GTID write watermarks, session stores, byte vs time lag, replica ejection, pri…

Saga pattern architecture

Deep-dive on the saga pattern: orchestration vs choreography, the durable saga log, compensating transactions and pivot placement, idempotency keys an…

Scaling patterns architecture

Deep-dive on scaling patterns: vertical, horizontal, stateless services, sharding, caching tiers, async, replicas, auto-scale.

Search System Architecture in Depth

A 2500-word walkthrough of search architecture: docs, indexer, inverted index, query, hybrid retrieval, reranking, personalization, analytics, shardin…

Service discovery architecture

Deep-dive on service discovery: the health-checked registry, client-side vs server-side discovery, DNS and mesh-sidecar packagings, watches and cachin…

Database sharding architecture

Deep-dive on database sharding: choosing the shard key, range versus hash partitioning, the routing layer and shard directory, online rebalancing, per…

Service Discovery Patterns

How microservices find each other in dynamic infrastructure.

Service Mesh Architecture

How a sidecar-based mesh separates business logic from cross-cutting concerns.

Shard Rebalancing Strategies

How to move data safely when adding, removing, or splitting shards.

Signal Protocol Architecture

How Signal's double ratchet gives forward secrecy and post-compromise recovery per message.

Slack Architecture

How Slack indexes billions of messages and delivers real-time updates to workspaces of thousands.

Snapchat Ephemeral Messaging Architecture

How Snapchat delivers self-destructing messages while enabling stories, filters, and multi-user features.

Spotify Music Streaming Architecture

How Spotify serves 100M+ tracks with personalized recommendations to 500M+ users.

Stock Exchange Matching Engine Architecture

How order matching engines process millions of orders/second with strict fairness + latency guarantees.

Stripe Payment Platform Architecture

How Stripe abstracts card networks, banks, and payment methods behind a clean API.

Backend for Frontend (BFF)

How BFF creates dedicated backend per client type (web, mobile) for optimized experience.

Bulkhead Pattern

How the bulkhead pattern isolates resources per dependency to prevent one failing dependency from consuming all resources.

Caching

The layers of caching in modern systems: CDN, reverse proxy, application cache (Redis), database query cache, and the eternal problem of cache invalid…

CDN

How CDNs cache content globally at edge nodes, cache invalidation, and modern edge compute (workers, functions).

Chat Application Design

How to design real-time chat: WebSockets, message ordering, delivery.

CQRS

How CQRS separates read + write models for independent scaling + optimization.

Event-Driven Architecture

How event-driven architecture decouples services via publishing + subscribing to events.

Event Sourcing

How event sourcing stores events as truth, deriving state by replay.

API Gateway Pattern

How API gateway provides single entry point with auth, rate limit, routing, caching.

Leader-Follower Replication

How leader-follower replication scales reads and provides failover.

Load Balancing

How load balancers distribute traffic across backend servers: L4 vs L7, round-robin vs least-connections, and health-check design.

Message Queues

The main message queue types (log-based Kafka vs broker-based RabbitMQ vs managed SQS), semantics (at-least-once vs at-most-once vs exactly-once), and…

Microservices Architecture

The microservices pattern: many small services vs monolith trade-offs.

Notification Service Design

How to design a scalable notification service (email, SMS, push).

Payment System Design

How to design a payment processing system: idempotency, ledger, reconciliation.

Rate Limiting

How rate limiting protects services from abuse: algorithms (token bucket, leaky bucket, sliding window), where to enforce, and cross-server coordinati…

Rate Limiter Design

How to design a distributed rate limiter.

Saga Orchestration

How saga orchestration coordinates long-running distributed workflows with compensations.

Search Autocomplete Design

How to design fast search autocomplete.

Service Discovery

How services find each other in dynamic environments: DNS-based, KV-store based (Consul, etcd), and Kubernetes service abstraction.

Sharded Architecture

How sharding partitions data across nodes for horizontal scale.

Twitter-Style Feed Design

How to design Twitter-style timeline (fanout on write vs read).

Uber-Style Rideshare Design

How to design a rideshare system: matching + routing + tracking.

Large File Upload Design

How to design large file upload: multipart, resumable, integrity.

URL Shortener Design

How to design a URL shortener like Bitly.

Video Platform Design (YouTube-Style)

How to design a video platform: upload, transcoding, streaming, recommendation.

Write-Ahead Log

How WAL provides durability by logging changes before applying them.

Telegram Architecture

Telegram's proprietary transport and its cloud-chat model that keeps messages accessible from any device.

TikTok Architecture

The For You Page algorithm and its real-time signal loop.

Twitter Timeline Generation Architecture

The fan-out patterns that make timelines feel real-time while scaling to hundreds of millions of users.

Uber Ride Matching Architecture

How Uber matches millions of riders to nearby drivers in seconds via geospatial indexing.

UPI Architecture

How UPI (Unified Payments Interface) processes 10B+ transactions/month via NPCI + Payment Service Providers.

Vector Search at Scale

How vector databases (Pinecone, Weaviate, pgvector) find nearest neighbors across billions of embeddings.

Video Streaming Architecture

How video-on-demand delivers adaptive quality to millions from a mesh of caches.

Website Hosting Architecture

The complete stack behind a modern static website with HTTPS, CDN, and DNS.

WeChat Super-App Architecture

How WeChat runs chat, payments, and 3M mini-apps inside a single app with 1.3B users.

WhatsApp Architecture

How WhatsApp delivers ~100 billion messages/day with end-to-end encryption and offline handling.

YouTube Architecture

How YouTube ingests, transcodes, stores, and delivers 4B+ hours of video daily.

Zoom Video Conferencing Architecture

How Zoom achieves low-latency multi-party video via SFU + regional data centers.