Just for some tip, You may use FreeBSD + ZFS if you need fast server with great caching. But hey that's still great achievement.
The nostr relay at wss://ftp.halifax.rwth-aachen.de/nostr just moved to new hardware, which is much faster. Give it a try!
The nostr database is served from a fast SSD (NVMe) based HW-RAID1.
With 20 GBit/sec of network connectivity, 256 GByte of RAM, and lots of CPU power, I believe speed shouldn't be an issue for the foreseeable future. If the storage demands grow, there's also around 30 TByte of HDD based disk space available.
Hardware details are available at https://ftp.halifax.rwth-aachen.de/