explaingit

clockworklabs/spacetimedb

📈 Trending★ 24,688RustAudience · developerComplexity · 4/5ActiveSetup · moderate

TLDR

A database that doubles as a server, letting you skip building a separate backend. Write your data and business logic directly in the database, and clients get real-time updates automatically.

Mindmap

mindmap
  root((SpacetimeDB))
    What it does
      Database plus server
      Real-time sync
      Skip backend layer
    Key concepts
      Modules
      Reducers
      Subscriptions
    Use cases
      Multiplayer games
      Collaborative tools
      Live dashboards
    Tech stack
      Rust core
      Multiple languages
    How it works
      In-memory state
      Disk persistence
      Auto push updates

Things people build with this

USE CASE 1

Build multiplayer games with real-time player synchronization without managing separate servers.

USE CASE 2

Create collaborative tools where changes made by one user instantly appear for all others.

USE CASE 3

Deploy live dashboards that push data updates to all connected clients automatically.

USE CASE 4

Skip DevOps infrastructure by running your entire backend as a single database module.

Tech stack

RustTypeScriptC#C++

Getting it running

Difficulty · moderate Time to first run · 30min

Requires installing a database server and understanding how to connect clients for real-time updates.

License could not be detected automatically. Check the repository's LICENSE file before use.

In plain English

SpacetimeDB is a relational database that also acts as a server, meaning you can skip building a traditional backend entirely. Normally, a web or game app needs three separate layers: a database, a server, and a client. SpacetimeDB collapses the first two into one. You write your data structure (called tables) and your business logic (called reducers) directly inside the database as a module, and clients connect to it straight. When data changes, SpacetimeDB automatically pushes those updates to every connected client in real-time, no polling, no manual refresh calls. The key concepts are modules (code you upload into the database), reducers (functions that act like API endpoints), and subscriptions (clients declare which tables they care about and get live updates when anything changes). All application state lives in memory for speed, while a log on disk ensures data survives crashes. You would reach for SpacetimeDB when building anything that needs real-time synchronization, multiplayer games, collaborative tools, live dashboards, and you want to avoid managing separate servers, containers, or DevOps infrastructure. The project's own MMORPG BitCraft Online runs its entire backend as a single SpacetimeDB module. The database is written in Rust. Modules can be written in Rust, C#, TypeScript, or C++.

Copy-paste prompts

Prompt 1
How do I write a reducer in SpacetimeDB to handle player movement in a multiplayer game?
Prompt 2
Show me how to set up a subscription in SpacetimeDB so my client gets real-time updates when a table changes.
Prompt 3
What's the difference between a module and a reducer in SpacetimeDB, and when would I use each?
Prompt 4
How do I deploy a SpacetimeDB module written in Rust or C# to production?
Prompt 5
Can I use SpacetimeDB to replace both my database and API server for a collaborative web app?
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Generated 2026-05-18 · Model: sonnet-4-6 · Verify against the repo before relying on details.