Please consider implementing indexing/search on multiple threads, to take advantage of SSD speed. This will greatly speedup operations on 10GB+ files.

My benchmarks. I have a Samsung 850 EVO SSD and both indexing and search are CPU-limited on a single thread. SSD read speed on a large file is ~340 MB/s for indexing and 210 MB/s for search of a short word. Benchmarked sequential read speed of my SSD is 450 MB/s. And there are NVMe SSDs on the market that have read speed on the order of 2-3 GB/s.

EmEditor btw is faster on both operations but still single-threaded CPU limited.