These are setting for a sever with a minimum of 16GB of RAM

Make sure no one is on the system. 

In pgAdmin select Tools > Server Configuration > postgresql.conf

Review the following 5 settings and make sure each of them has a tick in the box as illustrated below (some of them won't have a tick yet):

shared_buffers 512MB

work_mem 10MB

effective_cache_size 8GB

checkpoint_segments 32

checkpoint_completion_target 0.9

Note:  you can review other settings and options here:
Important changes from Spire 2 to Spire 3:

After inputting the new values then click on the green Play button (triangle) to update the configuration changes to the config file.

Open Services on the Server and stop the Spire API Service.

Restart the PostgresSQL service.

Start the Spire API Service again.

Test Spire Desktop behaviour.