Cobalt keeps recent writes in an in-memory skiplist backed by a write-ahead log, flushes them to immutable SSTables, and reclaims space through leveled compaction. Reads merge the memtable and every SSTable, honouring MVCC sequence numbers so snapshots and transactions observe a consistent view.

Features

Write-ahead log with single and batched frames, CRC framing, and torn-tail recovery.
Skiplist memtable with forward and reverse ordered cursors.
SSTable format with a block index, per-table bloom filter, RLE block compression, and CRC-checked blocks.
LRU block cache shared across readers.
MVCC snapshots and optimistic transactions with read/write conflict detection.
Leveled compaction that keeps levels disjoint and drops shadowed tombstones at the bottom level.
Forward, reverse, range, and prefix scans that merge all sources.
Atomic write batches and a manifest describing the level of each table.

Layout

File	Responsibility
`src/encode.zig`	byte encoding helpers, record and key types
`src/memtable.zig`	skiplist memtable and cursors
`src/wal.zig`	write-ahead log and replay
`src/sstable.zig`	SSTable builder, reader, and cursors
`src/bloom.zig`	bloom filter
`src/cache.zig`	LRU block cache
`src/compress.zig`	RLE block compression
`src/batch.zig`	write batches
`src/stats.zig`	database statistics
`src/txn.zig`	MVCC transactions
`src/db.zig`	store facade, compaction, and iterators
`src/main.zig`	command-line interface
`src/bench.zig`	throughput benchmark

Build

zig build            # build the library, cli, and benchmark
zig build test       # run the unit tests
zig build run -- <dir> <command> [args]
zig build bench -- [operations]

CLI

cobalt <dir> put <key> <value>
cobalt <dir> get <key>
cobalt <dir> del <key>
cobalt <dir> scan [start] [end]
cobalt <dir> rscan [start] [end]
cobalt <dir> prefix <prefix>
cobalt <dir> compact
cobalt <dir> stats
cobalt <dir> verify <n>