The purpose of this article is to highlight some of the differences between a Free and Professional tier Aura instances.
High Availability & Resilience
All Professional tier database instances benefit from high availability and resilience, while a Free tier instance does not. A Free tier instance is designed for you to rapidly learn, prototype and experiment without any friction or cost.
As part of the High Availability and Resilience in the Professional tier, features including replication of data across the cluster are provided. As a result of this it is not always favourable to compare the performance of a Free tier instance against that of a 1GiB Professional tier.
Page Cache Size
A Free tier database has a slightly larger page cache compared to that of the smallest 1GiB size Professional tier offering, this is due to the fact that Free tier instances do not benefit from the High Availability and Resilience features that are available in the Professional tier.
Liable to Change
A Free tier database is liable to change specs without prior notification due to it being a free offering.
Automatic Pausing & Deletion
A Free tier instance will be paused after a specific period of inactivity, if it is not resumed within a further period it will be deleted, as outlined in Why is my AuraDB Free Instance Paused ? A Professional tier instance does not have this same restriction.