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Database / Qdrant Vector DB Interview questions

What is memmap storage in Qdrant?

Memmap (memory-mapped) storage is a mode where Qdrant stores vector data in files on disk but accesses them through the operating system's memory-mapping mechanism, letting the OS transparently page data in and out of RAM as needed rather than requiring the entire dataset to be loaded into memory upfront.

In-Memory StorageMemmap Storage
All vector data loaded into RAM.Data lives on disk, mapped into memory on demand.
Fastest possible access, highest RAM requirement.Lower RAM requirement, some latency from disk access.
Best for collections that comfortably fit in available RAM.Best for collections larger than available RAM.

Because the OS handles the actual paging, frequently accessed data effectively stays cached in RAM over time (the OS's normal page cache behavior), so memmap storage doesn't necessarily mean every single query hits disk — it means the dataset can exceed available RAM without the process failing, with performance degrading gracefully as access patterns become less cache-friendly rather than the collection simply being unable to load at all.

What does memmap storage let a collection do that pure in-memory storage cannot?
What handles paging data in and out of RAM under memmap storage?

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