nn20db takes a different approach: it is a small C-based vector search engine for Linux and embedded devices, designed to search large persistent HNSW indexes from low-cost storage, including on devices such as the ESP32-P4.
The trade-off is intentional: nn20db favors large indexes, up to million-vectors, offline operation, low hardware cost, and good recall over maximum raw query speed. It is built for cases where the index is larger than available RAM and the device still needs to search locally.