db<>fiddle is free, and always will be. The engines (both VMs and micro VMs) run on a single 1U server bought in 2013 with a single E5-1650 (6c/12t) CPU and 32GB RAM. All the engines, but especially the Firecracker micro VMs could benefit from running on something faster.
If you or your company wants to donate a second-hand rack server (any U), please contact me here in the chat or privately with a DM [on Twitter](https://twitter.com/dbfiddleuk). Ideally 16 physical cores or less to match our Windows Server license for the SQL Server VM. No storage required, we can reuse our old S3700s which are still going strong.