From phpBB Development Wiki
When asking for help with performance, please provide the following information:
- Support request template.
- Size statistics: user, post, topic count, overall database size.
- Hardware information, if known (shared/dedicated hosting? Memory and cpu specs on the server?)
- Database type and for mysql engine/table type for phpbb tables.
Then, in phpmyadmin or mysql console run: "show full processlist" and post the complete output in the topic.