Upgrade WordPress SQL & Enable Caches

I need my WordPress site brought up to speed by upgrading the underlying SQL Server from version 5.7 to 8.0. The goal is a smooth transition with zero downtime if possible, but I’m open to your advice... (Budget: €30 - €250 EUR, Jobs: Database Administration, Database Design, Database Development, Database Management, MySQL, Performance Tuning, PHP, Redis, SQL, WordPress)