Few weeks ago I joined this meeting on the ‘multi-app environment’: one application was split into about six different apps. The arguments presented were:
1. maintainability – smaller apps are easier to maintain;
2. performance – smaller apps have smaller databases therefore performance is better;
3. continuity – if one app is down, the whole application need not be down.
Now, a few weeks later, I wonder whether these arguments are always valid. I fear that in many environments these arguments can be questioned.
Maintainability: the Mendix model allows one app to be split into several modules. This approach offers the
same advantages as split into several apps?
Performance: most database management systems contain intelligence to split files and tables into several parts and store these on (different parts of) different disks. 30 years ago it was already advised to developers to NOT split database because databases can and will do this better. Even different databases are managed within one big datapool by one databasemanagement-instance nowadays. I wonder whether the performance arguments hold.
Continuity: this argument certainly holds if the apps have no connection at all. However, in this case they would not be have been combined in the first place! Hardware failure also is not an issue, because shadow environments and replication are common processes in modern datacenters – so if there is a hardware failure the app keeps on running somewhere else. The only reason an app can really be down is because the software itself is not reliable. In that case the software testing and deployment process has a bug and the real question is: how to assure the quality of other apps and the quality of features that cover downage of the other apps. In financial companies the only possible decision is: if one is app down, the others have to shut down also – because of contingency and integrity and auditability requirements.
So, it is still not very clear to me why one would consider to split óne app into multiple apps. It seems to me it will create less performance and more risks