9.6 is the latest version of PostgreSQL incorporating a year's development effort and introducing major improvements to handling large amounts of data with new features like parallel query and reducing the need to continuously vacuum unmodified tables.
Aiven also lets you to fork an existing PostgreSQL 9.5 database into a new PostgreSQL 9.6 service. We're also planning to introduce in-place one-click upgrades of existing PostgreSQL 9.5 databases in the near future.
Remember that trying Aiven is free: you will receive US$10 worth of free credits at sign-up which you can use to try any of our service plans. The offer works for all of our services: PostgreSQL, Redis, InfluxDB, Grafana, Elasticsearch and Kafka!
Go to https://aiven.io/ to get started!