journald has never been of great quality. It somehow manages to be visibly slower than grepping gzipped text logs.

it has bad scaling properties esp. if you have many journal files

the last time I contributed to journald upstream was to fix a degenerate behavior with many journal files: https://github.com/systemd/systemd/commit/176f73272e6e3116ca...

that makes a dramatic difference for those hitting this case, but it only gets things from nearly unusable to slow-as-usual.