SNKV

A simple, crash-safe embedded key-value store

SNKV is a lightweight, ACID-compliant embedded key-value store written in C. It talks directly to SQLite's B-tree storage engine and skips the SQL layer: no parser, no query planner, no VM.

SQLite:  Application → SQL Parser → Query Planner → VDBE → B-Tree → Disk
SNKV:    Application → KV API → B-Tree → Disk

Looking for Python? The Python bindings are no longer maintained on master. Use the python_bindings branch.

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Quick Start

Single-header integration:

#define SNKV_IMPLEMENTATION
#include "snkv.h"

int main(void) {
    KVStore *db;
    kvstore_open("mydb.db", &db, KVSTORE_JOURNAL_WAL);

    kvstore_put(db, "key", 3, "value", 5);

    void *val; int len;
    kvstore_get(db, "key", 3, &val, &len);
    printf("%.*s\n", len, (char*)val);
    snkv_free(val);

    kvstore_close(db);
}

• API reference: hash-anu.github.io/snkv/api.html
• Examples: examples/ · hash-anu.github.io/snkv/examples.html

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Features

• ACID transactions and WAL mode (concurrent readers, single writer)
• Native TTL: per-key expiry, lazy eviction, bulk kvstore_purge_expired(). No background thread.
• Encryption: per-value XChaCha20-Poly1305 with Argon2id key derivation, transparent to all APIs
• Column families: logical namespaces within one database
• Iterators: forward and reverse, prefix, and seek
• Vector search: HNSW index via usearch (make vector), stored in the same .db file. See examples/vector.c.
• Thread-safe, single-header, Valgrind-clean
• Compatible with SQLite page/WAL-level tools such as LiteFS. Tools that need SQLite's schema layer (the sqlite3 CLI) do not work.

/* TTL */
kvstore_put_ttl(db, "session", 7, "tok123", 6, kvstore_now_ms() + 60000);

/* Encryption */
kvstore_open_encrypted("secure.db", "hunter2", 7, &db, NULL);

/* Custom configuration */
KVStoreConfig cfg = {0};                  /* zero fields are NOT defaults: set journalMode */
cfg.journalMode = KVSTORE_JOURNAL_WAL;
cfg.syncLevel   = KVSTORE_SYNC_FULL;
cfg.busyTimeout = 5000;
kvstore_open_v2("mydb.db", &db, &cfg);

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Build

Linux / macOS

make                  # libsnkv.a
make snkv.h           # single-header version
make examples         # build examples
make test             # run test suite
make vector           # libsnkv_vec.a (core + usearch, requires g++)
make test-vector      # run vector tests

Windows: use the MSYS2 MinGW 64-bit shell (not cmd.exe or PowerShell):

pacman -S --needed mingw-w64-x86_64-gcc make
make && make test

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Benchmarks

1M records on Linux. Both stores use WAL, synchronous=NORMAL, an 8 MB cache and 4 KB pages; SQLite uses a WITHOUT ROWID table. Source: SNKV · SQLite

Benchmark	SQLite	SNKV	Speedup
Sequential writes	142K ops/s	232K ops/s	1.64x
Random reads	90K ops/s	160K ops/s	1.77x
Sequential scan	1.56M ops/s	2.89M ops/s	1.85x
Random updates	16K ops/s	31K ops/s	1.9x
Random deletes	16K ops/s	31K ops/s	~2x
Mixed workload	34K ops/s	62K ops/s	1.79x

Comparisons against LMDB and RocksDB are available too.

Good fit: read-heavy or mixed workloads, native TTL (sessions, caches, leases), embedded or memory-constrained targets, and simple C integration. Consider alternatives: RocksDB for maximum write throughput, LMDB for maximum read speed when memory is plentiful.

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Third-Party Licenses

Library	License	Use
SQLite	Public Domain	B-tree, pager, WAL, OS layer (bundled)
Monocypher	CC0-1.0	XChaCha20-Poly1305 + Argon2id (bundled)
usearch	Apache 2.0	HNSW vector index (optional, make vector)

License

Apache License 2.0 © 2025 Hash Anu