Consistency of data between two databases on different server
If SQL server is the master,
LEt him insert first and get an id, this id you use to insert into mysql. As the sql server control ist. Mysql has an index on the id but is not a primary key., so you can insert what ever you need.
If both can generate the id, you must switch to uuids, these would always guarantee, that you are unique, and so it doesn't matter who generated the id first. as teh application generates the uuid, no autoincrrement is needed any more.
It will always be a good idea, to switch to other unique identifiers when mnore than one server is invooved.
The price is that the queries get slower, even with an index on the ids