For a single user, you can store all your notes on a Raspberry Pi. For 500 users, storage needs remain modest, around 2 GB per year. The main limitation of a Raspberry Pi is disk performance. High loads often occur due to I/O wait times. To achieve reliable performance, use a Raspberry Pi 5 with a PCIe NVMe adapter and NVMe drive. With a 100 GB NVMe disk, you could realistically run a full public relay.