What is BisonDB?

BisonDB is a single-node document database written from scratch in C++20, with a wire-protocol server, an interactive shell, and a desktop GUI. It exists to answer one question thoroughly: what does it actually take to build a database? — and to be a working, inspectable answer.

It is an educational and portfolio project. That framing is not an apology; it is a design constraint that shaped every component, and this site documents those components honestly.

What it does

• Stores BSON documents — the same binary format MongoDB uses. The codec passes the official BSON corpus tests for all 11 supported types and round-trips real mongodump files byte-for-byte.
• Indexes with a hand-written on-disk B+Tree — 4 KB slotted pages, order-preserving key encoding, page splits, crash recovery. No std::map behind the curtain, no storage libraries.
• Survives crashes — an append-only log is the source of truth; indexes are disposable caches that rebuild automatically after an unclean shutdown.
• Plans queries — equality and range filters use indexes when one exists, and explain() shows exactly what the planner chose and how many documents it touched.
• Speaks a real protocol — clients talk to bisond over TCP with length-prefixed BSON frames. The shell, the converter CLI, the GUI, and your own scripts all use the same protocol, documented completely.
• Encrypts and authenticates — since v1.2 the transport can run over TLS (--tls, TLS 1.2) and every connection must log in first. Users have one of three roles (read / readWrite / admin); passwords are Argon2id-hashed and sessions use in-memory tokens. The full model is on the Security page.

What it does NOT do

These are deliberate scope boundaries, not roadmap items hidden in fine print:

Not supported	What that means
Multiple nodes	No replication, no sharding, no consensus. One process owns one data directory.
Transactions	Single operations are atomic with respect to crash recovery; multi-document transactions don't exist.
Compound / unique secondary indexes	Indexes cover one field each; only _id is unique.
Field removal in updates	updateOne supports $set only.
TLS 1.3 / per-collection ACLs	TLS is 1.2 only; roles are server-wide, not per database or collection.
Production workloads	See the FAQ for an honest treatment of this question.

It does authenticate and encrypt (since v1.2) — that used to be on this list and no longer belongs here. See Security.

The pieces

Component	What it is
bisond	The server daemon.
bisonsh	Interactive shell with a Mongo-like statement grammar.
bisonc	BSON ⇄ JSON converter and embedded-mode CLI.
Prairie	A Tauri + React desktop GUI in the spirit of MongoDB Compass.

If you want to use it, start with the Quickstart. If you want to understand how it works inside — the better reason to be here — start with the architecture overview.