SQL Express has some limitations compared to the full MS SQL products. Even Infor suggests that a CRM system will run on SQL Express and it does, however, in a production environment, it’s usually not the 10gb database size limitation that gets you but rather the 1 GB database Engine limitation that will make for a very slow system.
So what is the “Database Engine” – The Database Engine component of SQL Server is the core service for storing, processing and securing data. The Database Engine provides controlled access and rapid transaction processing to meet the requirements of the most demanding data-consuming applications in your enterprise.
The more data from your database you can load into RAM as a buffer, the faster it will perform. Once that 1.4GB RAM (SQL Express limitation) is full it has to fetch data from a hard disk which is slower. As a comparison, the Standard edition of SQL Server can use 128GB RAM
Another significant limitation of SQL Express is Processors. Most Windows Servers today have more than one CPU/Processor and each processor can have multiple cores (like lots of mini CPUs on one chip). SQL Server Express can only ever use one of those processors, and if that processor has more than 4 cores (many now have 8), it can only use up to 4 of them. SQL Server Standard which can use 4 processors and up to 24 cores.