Cala
Cala is a robust ledger library developed by Galoy, designed to handle complex financial transactions and accounting operations. It provides a flexible and scalable solution for managing financial records with strong consistency guarantees.
Cala is distributed as a Rust library that you embed in your own service — it does not run as a standalone server.
Features
Core Capabilities
- Double-Entry Accounting: Built-in support for double-entry bookkeeping principles ensuring accurate financial records
- SQL-Compatible: Engineered to work with SQL databases (PostgreSQL) for robust data persistence and querying
- Strong Consistency: Ensures accuracy and reliability of financial records
- Real-time Processing: Efficient transaction processing suitable for production financial systems
API & Integration
- Rust Library: Embed the ledger directly in your Rust service via the
cala-ledger crate
- Transaction Templates: Customizable transaction templates for common financial operations, parameterized with CEL expressions
- Multi-Currency Support: Handle transactions across different currencies
- Event Sourcing: Persistent outbox for reliably streaming ledger events to downstream consumers
Usage
Add the dependency to your Cargo.toml:
[dependencies]
cala-ledger = "0.20"
Then initialize the ledger with a PostgreSQL connection pool:
use cala_ledger::{CalaLedger, CalaLedgerConfig};
let pool = sqlx::postgres::PgPoolOptions::new()
.max_connections(20)
.connect("postgres://user:password@localhost:5432/pg")
.await?;
let cala_config = CalaLedgerConfig::builder()
.pool(pool)
.exec_migrations(true)
.build()?;
let cala = CalaLedger::init(cala_config).await?;
For a complete working example — including creating accounts, transaction templates, and posting transactions — see examples/rust and run it with:
make reset-deps rust-example
Developing
Dependencies
Nix package manager
direnv >= 2.30.0
Testing
Run unit tests with:
make reset-deps next-watch
Errors
Cala uses errlanes for error handling.
