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DuckDB vs Alopex DB

DuckDB's columnar storage, vectorized execution, and how it handles concurrent writes. Also explains how it differs from Alopex DB.

Updated: Oct 11, 2026

What DuckDB is

DuckDB is an in-process SQL database for analytics. Like SQLite you open a file and run SQL, but DuckDB is columnar and aims to make aggregations and large scans fast.

How it works

  • Execution: push-based vectorized execution. A unit called a DataChunk is pushed through a tree of operators.
  • Storage: data is stored in row groups, a concept that parallels Parquet row groups. Parallelism and compression work per row group.
  • Concurrency control: In read-write mode, multiple threads in one process write at the same time. Appends never conflict. When two threads edit the same row at the same time, it detects a conflict. In read-only mode, multiple processes can read.
  • Isolation: the documentation says snapshot isolation is guaranteed, which is Repeatable Read in PostgreSQL’s terms. A transaction that violates it is aborted.

Main features

  • SQL for analytics. Columnar tables, reading and writing Parquet and other formats.
  • An extension system. Extensions such as vss are loaded with INSTALL and LOAD.

Limits

DuckDB itself handles writes from a single process only. Writing from multiple processes requires the beta Quack protocol or the separate DuckLake product. When two transactions update the same row at the same time, the later one fails with a conflict error. Row-by-row INSERTs are slow, and the documentation recommends loading data in bulk.

How it differs from Alopex DB

Both run inside your process and open a single file.

DuckDB is a columnar engine built to speed up aggregation and large scans. Alopex DB is a general-purpose engine that brings SQL, KV, and vector search together, and it handles columnar tables too. It suits an application that needs one database to hold it all.

DuckDB adds vector search through the vss extension. In Alopex DB, the HNSW index is in the core.

Alopex DB handles local analysis and app reads and writes in the same file. Run it once and see; the quickstart lets you check.

References