System Design

Animated explainers on system design.

All Caching & Performance Databases Kafka & Streaming Distributed Systems System Design Networking & Load Balancing ML & Agentic AI

System Design

May 18, 2026

The Complexity of Simple Writes

A user's single write action may trigger multiple downstream operations in a system, complicating consistency and overall system design.

System Design

May 11, 2026

Analytics Event Fan-Out: One Click, Seven Consumers, A Hundred Edge Cases

One user action becomes one event becomes seven downstream pipelines. The cost of that fan-out is schema evolution, lag, dedup, and per-consumer ordering.

System Design

Apr 28, 2026

Gray Failures: When the System Is Up and Broken at the Same Time

A node that returns 200s slowly is more dangerous than one that is fully down. Gray failures pass health checks, fool load balancers, and quietly poison everything that depends on them.

System Design

Apr 9, 2026

When Failover Is What Actually Causes the Outage

A region degrades, traffic shifts away, and the healthy regions collapse under the surge. Multi-region resilience is not about losing a region. It is about whether the survivors can carry the traffic.

System Design

Apr 3, 2026

Cascading Timeout Failures: Why Inverted Deadlines Multiply Load Under Stress

When timeouts grow as you go deeper into the call graph, slow downstreams keep doing work the client gave up on. Deadline propagation is the fix.

System Design

Mar 15, 2026

Token Bucket Rate Limiting: Bursts, Refills, and the Redis Trap

Token bucket allows bursts up to B and a sustained rate of R. Centralizing the bucket in Redis makes every API call a network hop, which scales until it doesn't.

System Design

Feb 28, 2026

Backpressure and Overload Control: Scale on Leading Signals, Not Lagging Ones

Retries and DLQs handle correctness. Backpressure handles survival. Without a signal from downstream, autoscaling on queue depth makes overload worse, not better.

System Design

Feb 27, 2026

SLOs and Error Budgets in Practice: Short Windows Beat Monthly Resets

An SLO is a target, an error budget is the runway. Monthly windows hide near-miss outages and create deploy freezes that ship even riskier code later.

System Design

Feb 27, 2026

Circuit Breaker Pattern: Stop Cascading Failures Cold

When a downstream service starts failing, the circuit breaker pattern stops you from taking everything else down with it. Closed, Open, Half-Open explained.

System Design

Feb 24, 2026

Retries, Timeouts, and Bulkheads: The Resilience Patterns That Only Work Together

Retries without timeouts cause storms. Timeouts without bulkheads let one slow dependency drain your pool. These patterns are a system, not a menu.

System Design

Jan 15, 2026

Redis Is Single-Threaded and Still Has Race Conditions

Single-threaded does not mean race-free. Here is why GET-then-SET breaks under concurrency, and how Lua scripts, WATCH/MULTI/EXEC, and SETNX restore correctness.

System Design

Dec 20, 2025

Why Microservices Fail: The Distributed Monolith Trap

Microservices do not fail because the pattern is wrong. They fail because teams split the code without splitting the ownership, and end up with a distributed monolith that ships slower than the original.

System Design

Dec 19, 2025

Serverless Architecture Explained: It Is Not No Architecture

Serverless does not mean architecture-free. It means your architecture moves into IAM, API Gateway, Lambda, Step Functions, and EventBridge config, where cold starts and concurrency limits are first-class constraints.

System Design

Dec 7, 2025

Access Tokens and Refresh Tokens: Why You Need Both

Access tokens are short-lived bearer credentials sent on every API call. Refresh tokens are long-lived and only ever leave storage to exchange for new access tokens. Mixing up where each one lives is how accounts get drained.

System Design

Nov 26, 2025

Web Crawler System Design: Politeness Is a Sharding Problem

A web crawler is a URL frontier, a fetcher pool, a parser, a dedup layer, and storage. The hard part is not any one component. It is enforcing per-host politeness when the crawler is sharded across many nodes.