Aiven offers both PostgreSQL and MySQL as managed services. While similar, they meet different needs. Both databases support some NoSQL features and are open-source systems. The choice between them depends on various factors such as applications, conformance to SQL standards, languages and data types supported, performance/speed, user interfaces, extensions, data security and authentication, coding, and support. PostgreSQL is a good choice for developers requiring rich feature sets and administrators needing protected, fault-tolerant environments. MySQL is suitable for those needing a fast, lightweight, customizable database solution with an active community for support.