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nexus_db

embedded LSM key-value store in C++17, with a live telemetry dashboard.

readme

An embedded key-value store written in C++17, taking its architecture from LevelDB and RocksDB: writes land in an in-memory skip list, get durability from a write-ahead log, and are flushed to immutable SSTables on disk. On top of the engine sits a FastAPI layer talking to the C++ core over a ctypes FFI, and a React dashboard showing live telemetry.

signal log

• MemTable is a probabilistic skip list, giving O(log n) insert and point lookup with no tree-rebalancing overhead.
• write-ahead log appends every operation to disk before the MemTable is touched, recording intent ahead of effect.
• MemTable freezes and flushes to an immutable SSTable via sequential write once it passes 1 MB.
• deletes write tombstone markers rather than removing data: SSTables are immutable, so the marker is what makes the newest-first read report a miss.
• SSTables are re-adopted on open and the file counter resumes past the highest index, so reopening a database does not shadow or overwrite what is already on disk.
• three-layer stack: C++17 engine, Python/FastAPI REST API over ctypes FFI, React/TypeScript dashboard.
• not yet built: WAL replay on startup, compaction, and per-file indexes. reads scan each SSTable linearly.

built with