# The Architecture without TiDB

![`smart`](./student-guide/diagram/ArchBeforeTiDB_en_001_20220721.png)

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Use MySQL for online transaction processing.

With the read-replicas, the architecture can handle a pretty serious load. 

Use Cache for transit session level object to improve performance.

Although NoSQL is an ideal choice for horizontal scalability in a persistent storage system, it lacks SQL compatibility.  

The architecture of the data layer is complex to a certain degree.