memista vs USearch (direct)
memista uses USearch as its vector index. The honest comparison is therefore not “library A vs library B” — it is “do I want USearch by itself, or with the metadata layer, persistence helpers, and HTTP service memista wraps around it?“
| dimension | memista 0.1.x | USearch 2.19.x (direct) |
|---|---|---|
| Layer | Library + bundled HTTP server | Library only |
| Vector index | USearch (transitive) | USearch (native) |
| Metric available | IP (hardcoded in IndexOptions) | IP, Cosine, L2, Hamming, Tanimoto, Sorensen, Haversine, Divergence |
| Quantization | F32 (hardcoded) | F32, F16, F64, BF16, I8, B1 |
| Embedding dimensions | hardcoded to 2 in current crate | runtime-set |
| Metadata storage | SQLite (chunks_<db_id> table) | none — you bring your own |
| Multi-tenant | by database_id (one table + one index file each) | by separate index instances |
| HTTP API | /v1/insert, /v1/search, /v1/drop via Actix-web | none |
| OpenAPI / docs UI | yes — apistos + Swagger / Redoc / RapiDoc / Scalar | none |
| Persistence | SQLite WAL + <db_id>.usearch file | .usearch file (you call save / load) |
| Async | yes (tokio, async-sqlite, actix-web) | sync core, async wrappers available |
| Tuning surface | accepts USearch defaults (connectivity: 0, expansion_*: 0) | full IndexOptions exposed |
| Status | experimental (per README) | production at Unum |
| License | GPL-3.0 | Apache-2.0 |
When to pick USearch directly
- You only need the vector index. You already have a place for metadata (an existing Postgres, a flat file, whatever) and don’t want a second database in the picture.
- You need to tune
connectivity,expansion_add,expansion_search, or use a non-IP metric, or quantize tof16/i8/b1. memista’s currentload_or_create_indexdoes not expose these. - You want the full set of distance metrics — cosine, L2, Hamming. memista
uses
MetricKind::IPin the source; cosine via IP requires you to normalize vectors yourself before insertion, which memista does not do. - License: USearch is Apache-2.0. memista is GPL-3.0, which is meaningful if you ship a proprietary binary.
When to pick memista
- You want HTTP-out-of-the-box. memista gives you an Actix-web server with
OpenAPI documentation rendered four ways at
/swagger,/redoc,/rapidoc,/scalar. USearch does not. - You want SQLite-backed metadata storage already wired up. memista creates
a
chunks_<database_id>table per logical partition, inserts text and metadata, and joins index hits back to rows for you. With USearch direct, you write that layer. - You want multi-tenant isolation by
database_id. memista’s pattern of one SQLite table and one.usearchfile per partition is in the box. - You are prototyping. The combination of “single
cargo install,” REST endpoints, andsqlite3 memista.dbfor inspection is the fastest way to a working RAG demo in Rust.
What memista does not do that USearch does
- Expose all metrics. Hardcoded to IP.
- Expose quantization choices. Hardcoded to F32.
- Expose tuning parameters. Passed as
0(USearch defaults). - Accept arbitrary embedding dimensions. Hardcoded to
2insrc/lib.rs. You will edit this; a real release should make it configurable fromIndexOptionsperdatabase_id. - Run at the scale USearch is tested at. memista’s README states it has not been tested past ~100k vectors.
What USearch does not do that memista does
- Bind to a port and serve HTTP.
- Persist metadata.
- Render OpenAPI documentation.
- Provide multi-tenant partitioning by string ID.
The honest summary
memista is a convenience wrapper. If you want the convenience — SQLite plus HTTP plus OpenAPI plus partitioning, in one crate — it earns its keep. If you want the full power of USearch and don’t need a service shape, use USearch directly. The two are not really competitors; memista is a configuration of USearch with batteries.
Sources: src/lib.rs and Cargo.toml in this repository; USearch
documentation at https://github.com/unum-cloud/usearch.