SYMPTOM
Settings within AtScale can affect one another. One of these instances is the JDBC connection settings and the aggregate creation concurrency settings. There must be sufficient JDBC connections for the aggregate settings and additional overhead for the engine to run health checks and other internal items.
RESOLUTION
Under SETTINGS --> Engine, users can control the number of JDBC connections with the setting CONNECTION.POOL.GROUP.MAXCONNECTIONS. This setting must be high enough to accommodate overhead and the settings under Aggregates, which can be found under SETTINGS -->Aggregate Settings-> CONCURRENT QUERIES PER ORGANIZATION.
If the pool is not large enough to accommodate the concurrency and overhead, queuing of requests will be seen in the logs and can cause engine issues, resulting in batch failures. The best practice is to have a larger pool than the concurrency.