How We Upgraded PostgreSQL at GitLab.com

We explain the precise maintenance process to execute a major version upgrade of PostgreSQL. The biggest challenge was to do a complete fleet major upgrade through an orchestrated pg_upgrade. We needed to have a rollback plan to optimize our capacity right after Recovery Time Objective (RTO) while maintaining a 12-node clusterâs 6TB-data consistent serving 300.000 aggregated transactions per second from around six million users.

The best way to resolve an engineering challenge is to follow the blueprints and design docs. In the process of creating the blueprint, you define the problem that we are attempting to solve, evaluate the most suitable solutions, and consider the pros and cons of each solution. Here is a link to the blueprint from the project.

After the blueprint comes the design process. The implementation is detailed in the design process, where we explain the steps and requirements involved in executing the design. The design doc from the project is linked here.

Source: gitlab.com