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Architecture Overview

ScramDB is an adaptive HTAP SQL database written in Rust.

How a Query Executes​

SQL Query
  → PostgreSQL Wire Protocol
    → SQL Parser
      → Cost-Based Optimizer
        → Bytecode Compiler
          → JIT Compiler (background)
            → Parallel Execution (core-pinned workers)
              → Results (streamed via PgWire)

Key Design Decisions​

JIT Compilation​

ScramDB compiles SQL queries to native machine code to native machine code instead of interpreting them. Queries are transparently compiled in the background - no configuration needed. Compiled code is cached to disk and reused across restarts.

Morsel-Driven Parallelism​

Each query is split into pipelines that process data in parallel "morsels." Workers are pinned to CPU cores for zero-overhead scheduling and linear scaling.

Tundra Columnar Storage​

Custom columnar storage engine with zone maps for automatic predicate pushdown, buffer pool caching, CRC32C integrity, and WAL-based crash recovery.

Transactions​

Full MVCC with PostgreSQL-compatible isolation levels: Read Committed, Repeatable Read, and Serializable.

Indexing​

Three index types: ART for point lookups, B+Tree for range queries, and Hash for equality checks. The optimizer automatically selects the best access path.

PostgreSQL Compatibility​

Full PostgreSQL wire protocol - connect with psql, JDBC, psycopg2, or any PG driver. Standard SQL syntax, not a custom query language.