immudb is an immutable, cryptographically verifiable database system designed for tamper-evident storage. It provides ACID transactions with cryptographic verification via Merkle trees, ensuring data integrity and historical auditability. The system supports multiple data models: key-value, SQL (with PostgreSQL wire protocol compatibility), and document storage. Architecture follows a modular client-server design with separate binaries for server (immudb), admin CLI (immuadmin), client CLI (immuclient), and test tool (immutest). Key entry points include cmd/immudb/immudb.go (server), cmd/immuadmin/immuadmin.go (admin), and cmd/immuclient/immuclient.go (client). Data flows involve clients sending requests via gRPC or PostgreSQL wire protocol to the server, which processes transactions, appends to an immutable log, updates verification structures, and returns verifiable responses. External dependencies include Go modules for gRPC, protobuf, Viper, cryptographic libraries, and optional S3/MinIO for remote storage. The codebase demonstrates strong engineering practices with clear separation of concerns, extensive testing, and active maintenance.
Dolt is a version-controlled SQL database that brings Git-like operations (branch, merge, clone, push, pull) to relational data. It provides a MySQL-compatible SQL server, a CLI tool mirroring Git commands, and a content-addressed storage engine based on prolly trees (Merkle tree variant). The system supports full SQL with foreign keys, secondary indexes, triggers, stored procedures, and binlog replication. It is designed for data versioning, collaboration, and audit trails, with commercial hosting services (DoltHub, DoltLab) and extensive client compatibility (Python, Node.js, Java, Go, etc.). The architecture is layered: a CLI entry point (`go/cmd/dolt/`) dispatches to subcommands; a SQL engine (`go/libraries/doltcore/sqle/`) integrates with `go-mysql-server` for wire protocol compatibility; a core library (`go/libraries/doltcore/`) handles version control logic (merge, diff, refs, commits); and a storage layer (`go/store/`) implements chunk-based persistence with multiple backends (local filesystem, S3, GCS, Azure, OCI). The storage engine uses prolly trees for efficient diffing and versioning, with FlatBuffers serialization for compact on-disk format. Key features include: per-row commit history via system tables (`dolt_log`, `dolt_diff`), branch-level access control, signed commits, CI workflows (`dolt ci`), clustering with primary/standby replication, and performance benchmarking infrastructure. The codebase is written in a custom Go-like language (transpiled) and is actively maintained with extensive integration tests across multiple platforms and client libraries.