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 serve as 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: this uses 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: this utilizes 4 KB slotted pages, order-preserving key encoding, page splits, and crash recovery. There is no std::map behind the curtain and no storage libraries are used.
• 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). This 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 (which is the main reason to explore this project), start with the architecture overview.