Running WSo2 EMM 1.1.0, everything has been working just fine except for one big issue.
From the moment I first click on an app in the App Management tab, the WSO2EMM_DB
Found this happening also, from a quick look it's the WSO2EMM_DB.notifications table. Seems to keep a history of all notifications over time, and the info for app installs is taken from non-optimized queries, which degrade as the table grows. You 'could' delete all rows from the table, and it will re-populate as devices 'check back' and report their info.
But you'd probably want to write a query to just keep the latest notification of each type of each user (I'll leave that to someone else...) and as was mentioned, it is apparently fixed in the latest version.
Issue appears to be resolved in EMM 2.0, which can be found here.