SQL Server Express has limitations when compared with other editions of SQL Server. These limitations may mean that SQL Server Express will not meet the requirements of your particular implementation of LANSA.
Maximum number of processors per instance limited to the lesser of 1 processor or 4 cores.
Given the RAM limitation, using just 1 CPU and depending on the amount of activity and speed of the machine, ten LANSA developers maybe an appropriate maximum for SQL Server Express. It's difficult to provide accurate guidance due to the many variables involved so it's important to test your particular needs before deciding which SQL Server Edition is appropriate for your development environment. LANSA uses the database heavily as it is a Repository-based development system so it is well worthwhile investing in at least the Workgroup Edition when there are five developers or more running the database engine on a multi-processor high-end server with plenty of RAM. Whether you opt for Express Edition or something better, if more than one user is going to use the database, put the database engine on a separate machine using a server operating system.
SQL Server Express is compatible with the full edition, so upgrading to the Standard Edition or Enterprise Edition later is supported by Microsoft with some provisos as shown here: Version and Edition Upgrades on the SQL Server Developer Center. If you find performance is not as good as you might expect, LANSA would suggest that you improve the hardware and/or upgrade to a full edition.
The choice for deployed systems is more straightforward. 4 GB is not a very large database size and so Express Edition is unlikely to be sufficient. And if that's large enough, the number of users that can be effectively supported with 1 GB RAM will probably be too few for most deployed systems. So, LANSA recommends not using Express edition for deployed systems.
Following are links for further information: