What is a hybrid memory model?

A hybrid memory model, or architecture, is when the index is purely in-memory and not persisted. Data is stored only at persistent storage (SSD) and read directly from the disk. Disk I/O is not required to access the index, which enables predictable performance.

This hybrid memory model is possible because the read latency characteristic of I/O in SSDs is the same. This is regardless of whether it’s random or sequential. For such a model, optimizations described are used to avoid the cost of a device scan to rebuild indexes.