SpacetimeDB

SpacetimeDB is a database that allows developers to write their entire application as a database module. Server-side logic is executed directly inside the database as WebAssembly (Wasm) modules. This architecture removes the need for a separate application server. Clients interact with the database by subscribing to queries and receiving real-time updates over a WebSocket connection.

SpacetimeDB is a database that allows developers to write their entire application as a database module. Server-side logic is executed within the database as WebAssembly (Wasm). Instead of traditional REST or GraphQL APIs, clients subscribe to queries and receive real-time data updates over a WebSocket connection, removing the requirement for a separate backend server.

SpacetimeDB allows binary data (blobs, images, files) to be stored directly in table columns. This ensures that binary assets can participate in database transactions and subscriptions.

Reducers are functions that modify database state in response to client requests or system events. They are the exclusive mechanism for mutating tables in SpacetimeDB; all database changes must be performed through a reducer. Every reducer receives a special context parameter as its first argument, which provides read-write access to the database, information about the caller, and utilities such as random number generation.

Tables are the primary mechanism for storing data in SpacetimeDB. All data is stored in-memory to ensure extremely low latency and high throughput, while the system automatically persists all data to disk for durability.

Views are read-only functions used to compute and return results from tables. Unlike reducers, views cannot modify database state. They are primarily used for computing derived data, performing aggregations, or joining multiple tables before returning the results to clients.

Event Tables are used to notify clients about occurrences (e.g., combat damage in a game) without storing that information permanently in the database. This is ideal for real-time systems where data is only relevant at the moment it happens.

A procedure is a function exported by a SpacetimeDB database. It is similar in nature to a reducer.

Data in SpacetimeDB is stored in Tables. For low latency and high throughput, all data is kept in memory, but it is automatically persisted to disk. Durability is ensured via a commitlog (write-ahead log), which records every committed transaction. The full state of a database can be reconstructed by replaying this log.

SpacetimeDB is a platform that integrates application logic, relational data, authentication, and live synchronization into a single system. To build effectively with Spacetime, developers should focus on the interaction between the following core components: tables, reducers, subscriptions, generated bindings, and SpacetimeAuth.

Event Tables are used to notify clients about occurrences (e.g., combat damage in a game) without storing the information permanently in the database. This is ideal for real-time systems where data is only relevant at the moment it happens.

Tables are the primary mechanism for storing data in SpacetimeDB. All data is stored in memory to ensure extremely low latency and high throughput, while the system automatically persists all data to disk for durability.