Disk-based and in-memory algorithms and data structures need similar techniques these days. The numbers are just different. RAM latency is something like 100 n

Disk-based and in-memory algorithms and data structures need similar techniques these days. The numbers are just different. RAM latency is something like 100 ns, or maybe a bit less. Sequential read speed ranges from tens to hundreds of gigabytes per second. However, if you divide cache line size by latency, you are still orders of magnitude below that. If an algorithm accesses the memory randomly and waits for the results before continuing, it's often much slower than an algorithm that reads sequentially, even when the structs are conveniently the size of a cache line. SSD read latency is around 100 µs, or three orders of magnitude higher. Sequential read speed is gigabytes per second, or 1-2 orders of magnitude lower. Again, if you divide page size by latency, you are nowhere near the peak throughput. Reading sequentially can be much faster, because the OS and the controller can guess your intent and read ahead.