Crate flowdb 

FlowDB — an embedded LSM-tree storage engine with a built-in JSON document database.

Overview

FlowDB is a high-performance embedded storage engine written in Rust, powered by an LSM-tree architecture with WAL, SSTables, and Bloom filters. It includes JsonDB, an IndexedDB-compatible JSON document layer with ACID transactions and secondary indexes.

Fully synchronous API — no async runtime required. FlowDB uses plain OS threads for background maintenance, making it runtime-agnostic.

LSM Engine

The core engine (Engine) provides a key-value store where each record has a binary key, microsecond timestamp, expiry time, and binary value. It supports point lookups, prefix scans, range queries, time-range queries, lazy iterators, and batched writes.

use flowdb::{Engine, Config, Record, Query};

let engine = Engine::open(Config::default()).unwrap();
engine.write_batch(&[Record::new("key", 1_700_000_000_000, b"value".to_vec())]).unwrap();
for result in engine.query(Query::prefix("key")).unwrap() {
    println!("{}", result.key_str());
}
engine.shutdown().unwrap();

JsonDB Document Layer

JsonDB is a document database built on top of the LSM engine, providing an IndexedDB-like API with object stores, secondary indexes, ACID transactions, and serde integration.

use flowdb::jsondb::{JsonDB, StoreSchema};
use serde_json::json;

let db = JsonDB::open(Default::default()).unwrap();
db.apply_store(&StoreSchema::new("users", "id")
    .with_index("by_email", &["email"], true)
).unwrap();
db.put("users", json!({"id": "u1", "email": "a@b.com"})).unwrap();
let doc = db.get("users", &json!("u1")).unwrap();

When to use FlowDB

• Embedded databases — no server process, no external dependencies
• Edge Functions / Serverless — embed directly in Wasm or VM functions
• IoT / Time-series — efficient time-bucketed index and TTL expiry
• Offline-first apps — local-first with eventual sync to remote
• Testing — fully isolated backend without Docker or network I/O

Re-exports

pub use engine::Engine;

pub use engine::MaintenanceHandle;

pub use engine::ScanIterator;

pub use error::FlowError;

pub use error::Result;

pub use record::Config;

pub use record::KeyFilter;

pub use record::Op;

pub use record::Query;

pub use record::ReadOptions;

pub use record::Record;

pub use record::ScanRange;

pub use record::StorageBackendKind;

pub use record::SyncMode;

pub use stats::EngineStats;

Modules

cache

engine

error

jsondb

JsonDB – A JSON document database interface built on top of FlowDB.

record

stats

Derive Macros

ObjectStore

Derive the ObjectStore trait for a struct.