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Build-your-own-X

Build your own real system.

Leetcode for system design.

Choose a trackBrowse 150+ tutorials

No coding necessary

166
tutorials
5
live tracks
35
modules

Choose your system

Build it yourself.

Pick the system you already use—or the one you have always wanted to understand. Each track builds up gradually until you have a whole production architecture.

RDS Published

Build your own

Redis

Redis-inspired in-memory data store built from key-value command execution through protocol handling, storage internals, persistence, replication, failover, and cluster sharding.
  • event loop
  • persistence
  • replication
  • sharding
24 tutorials10 modules
Start this track Free account required · we’ll save your destination
Complete curriculumRedis field manual
24 tutorials · 10 modules

01Single-node Core

  1. 01Single-Node Key-Value Core

02Network Protocol

  1. 02RESP Protocol Parser
  2. 03Client Connection Lifecycle

03Execution Core

  1. 04Event Loop
  2. 05Command Table And Dispatch

04Data Model

  1. 06Redis Object Model
  2. 07Hash Table And Rehashing
  3. 10Core Data Types

05Memory Lifecycle

  1. 08Expiration System
  2. 09Memory Limits And Eviction

06Command Behavior

  1. 11Pipelining And Output Buffers
  2. 12Transactions
  3. 13Scripts/functions
  4. 14Pub/Sub
  5. 15Streams

07Persistence

  1. 16RDB Snapshotting
  2. 17AOF Persistence
  3. 18Startup Recovery

08Replication And Failover

  1. 19Replication: Full Sync
  2. 20Replication: Partial Sync
  3. 21Failover Controller

09Clustering

  1. 22Cluster Sharding
  2. 23Cluster Resharding

10Capstone

  1. 24track Redis-Like System

Why this exists

System design is always taught passively.

Most resources ask you to read an explanation, look at some diagrams, and move on. You never find out what you actually understand—or try to design something yourself.

fivenines lets you do the designing. Receive instant feedback on what works and improve at the lightning speed.

Choose your system
The usual waypassive
  1. Read the explanation
  2. See how someone solved it
  3. Move on with no actionable feedback
With fiveninesbuild it yourself
Read a conceptPractice until you understand itDesign a system with itImprove & revise until you solidify it
feedback right away

The feedback

Every diagram gets graded.

submissionprice-time-matching.d292 / 100
Runtime path

Gateway → risk → matching is explicit.

Failure mode

Replay path restores the order book.

Invariants

Price-time priority stays deterministic.

Trade-offs

Name the latency cost of synchronous risk.

PASS

Keep the mechanism. Fix one trade-off.

Coming soon

The library keeps expanding.

The same build-from-first-principles method is moving into distributed data, infrastructure, observability, AI systems, and the products engineers use every day.

Data systems

Build your own Kafka

Track in development

Data systems

Build your own SQLite

Track in development

Developer tools

Build your own Git

Track in development

Infrastructure

Build your own Kubernetes

Track in development

Infrastructure

Build your own Terraform

Track in development

Infrastructure

Build your own NGINX

Track in development

Cloud systems

Build your own S3

Track in development

Observability

Build your own Prometheus

Track in development

Observability

Build your own OpenTelemetry

Track in development

AI systems

Build your own LLM Inference

Track in development

AI systems

Build your own Agent Runtime

Track in development

AI systems

Build your own Vector Database

Track in development

Web platform

Build your own Web Browser

Track in development

Identity

Build your own OAuth Server

Track in development

AI systems

Build your own MCP Server

Track in development

Product systems

Build your own Slack

Track in development

Product systems

Build your own YouTube

Track in development

17 tracks currently on the roadmap.

Sign in to vote for what ships next →

Pricing

Start free. Upgrade when hooked.

Free€0
  • Theory and practice across every track
  • First three design problems in every track
  • Five AI reviews for each free design problem
  • Saved learning progress when signed in
  • No card needed
Choose a track
Pro€29/mo
  • Everything in Free
  • Every build-your-own design problem
  • D2 workspace + AI-powered feedback
  • €199 / year
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TeamsCustom
  • Team seats
  • Shared learning paths
  • Private onboarding
Contact us

FAQ

Five useful answers.

Everything you need before choosing your first system.

01Is this a system design interview course?

No. It can help with interviews, but the main goal is to understand how real systems work and why engineers make particular design choices.

02Do I need to write production code?

No. You work with short lessons, practical questions, and D2 architecture diagrams. The focus is explaining and improving the design.

03Which track should I start with?

Choose the system closest to your current work or the one you are most curious about. Every track starts with its core promise and builds from there.

04What can I try for free?

Theory and practice are open across every published track. Sign in to build the first three design problems in each track and get five AI reviews for each one.

05How does the feedback work?

Your diagram is checked against the tutorial’s own rubric. The review points to the specific mechanism, guarantee, or trade-off that needs another pass.

Pick your machine

Stop memorizing.
Start building.

Choose a track