Hello @MrSky ,
Welcome to the Microsoft Q&A platform.
1) How many total databases can I house under a single ADX cluster?
Number of databases in a cluster – 10000
2) What is the maximum combined size of databases I should plan to house a single ADX cluster?
There is no limit on maximum combined size of databases.
3) Any performance constraints if add all 50 databases under one single cluster?
There are no performance constraints.
The following table describes the maximum limits for Azure Data Explorer clusters.
The following table describes the limits on management operations performed on Azure Data Explorer clusters.
Hope this helps. Do let us know if you any further queries.
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