# Solution 1: Heterogeneous databases
+ Issue with this solution
  + Complicated Architecture 
  + Hard to scale
  + Poor performance
  + Hard to maintain

![`smart`](ResourceControlCaseStudyOldArch_aa_001_20240502.png)
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When multiple database are used, the architecture becomes too complicated. For some modules, standalone MySQL databases are used. For some modules with large amount of data, sharded MySQL databases are used. For some situations with documentation data, MongoDB is used.

Both standalone MySQL and sharded MySQL are hard to scale.

Due to the complicated architecture, some sophisticated queries may take more than 10 seconds to response, which is unacceptable to individual customers.

It is hard for the operation team to maintain this data architecture.