Mini-LSM: Build a Database Storage Engine in Rust

Mini-LSM is a hands-on course in database internals for systems and backend engineers. Build an LSM-tree storage engine from memtables and SSTs through compaction, crash recovery, MVCC, and transactions.

Start the guided three-week course · Try the coding-agent track

Week 1 produces a working storage engine. Weeks 2 and 3 add production-inspired compaction, durability, concurrency control, and multi-version transactions.

What You Will Build

By the end of the course, your engine will include:

• an ordered in-memory write buffer and immutable SST files;
• point lookups and range scans over merged memory and disk state;
• multiple compaction strategies and background maintenance;
• a manifest and write-ahead log for crash recovery; and
• snapshots, MVCC garbage collection, optimistic concurrency control, and serializable validation for tracked keys.

Mini-LSM focuses on the storage layer of a database. It does not cover SQL parsing, query optimization, replication, or distributed consensus.

Choose a Learning Path

Path	Best for	Format	Status
Guided course	Learners who want to implement and reason through each subsystem	Three weeks, with seven chapters per week	Complete
Coding-agent track	Learners who want an agent to handle mechanical implementation without outsourcing system design	Three planned days built around decision stops, focused code slices, and adversarial tests	Days 1–3 available

You need basic Rust, but you do not need prior knowledge of LSM trees, compaction, MVCC, or transaction isolation. The course is a good fit if you have used systems such as PostgreSQL, MySQL, Redis, or RocksDB and want to understand what happens below their APIs.

Community

You may join skyzh's Discord server and study with the mini-lsm community.

Add Your Solution

If you finished at least one full week of this course, you can add your solution to the community solution list at SOLUTIONS.md by submitting a pull request.

Development

For Students

You should modify code in mini-lsm-starter directory.

cargo x install-tools
cargo x copy-test --week 1 --day 1
cargo x scheck
cargo run --bin mini-lsm-cli
cargo run --bin compaction-simulator

For Course Developers

You should modify mini-lsm and mini-lsm-mvcc

cargo x install-tools
cargo x check
cargo x book

If you changed public API in the reference solution, you might also need to synchronize it to the starter crate. To do this, use cargo x sync.

Code Structure

• mini-lsm: the final solution code for <= week 2
• mini-lsm-mvcc: the final solution code for week 3 MVCC
• mini-lsm-starter: the starter code
• mini-lsm-book: the course

We have another repo mini-lsm-solution-checkpoint at https://github.com/skyzh/mini-lsm-solution-checkpoint. In this repo, each commit corresponds to a chapter in the course. We will not update the solution checkpoint very often.

Demo

You can run the reference solution by yourself to gain an overview of the system before you start.

cargo run --bin mini-lsm-cli-ref
cargo run --bin mini-lsm-cli-mvcc-ref

And we have a compaction simulator to experiment with your compaction algorithm implementation,

cargo run --bin compaction-simulator-ref
cargo run --bin compaction-simulator-mvcc-ref

Guided Course Structure

The guided course has three complete weeks.

• Week 1: Storage Format + Engine Skeleton
• Week 2: Compaction and Persistence
• Week 3: Multi-Version Concurrency Control
• The Rest of Your Life: Closing chapter with expansion paths

Week + Chapter	Topic
1.1	Memtable
1.2	Merge Iterator
1.3	Block
1.4	Sorted String Table (SST)
1.5	Read Path
1.6	Write Path
1.7	SST Optimizations: Prefix Key Encoding + Bloom Filters
2.1	Compaction Implementation
2.2	Simple Compaction Strategy (Traditional Leveled Compaction)
2.3	Tiered Compaction Strategy (RocksDB Universal Compaction)
2.4	Leveled Compaction Strategy (RocksDB Leveled Compaction)
2.5	Manifest
2.6	Write-Ahead Log (WAL)
2.7	Batch Write and Checksums
3.1	Timestamp Key Encoding
3.2	Snapshot Read - Memtables and Timestamps
3.3	Snapshot Read - Transaction API
3.4	Watermark and Garbage Collection
3.5	Transactions and Optimistic Concurrency Control
3.6	Serializable Snapshot Isolation
3.7	Compaction Filters

Related Projects

mini-lsm inspired several projects used in production.

• SlateDB is an LSM engine over the object storage system.
• Tonbo stores parquet files directly on the object storage and organizes them in an LSM tree structure.

License

The Mini-LSM starter code and solution are under Apache 2.0 license. The author reserves the full copyright of the course materials (markdown files and figures).