Multiple concurrent sql dumps in mysql
In general terms is safe as long as the databases are "independent". With this I mean each database has references only to itself. 

For MySQL in particular VIEWs to missing tables are a problem.

Let me illustrate with an example:

create schema database1;
create table database1.mytable (id int);
create schema database2;
create view database2.myview as select * from database1.mytable;


We take separate dumps: database1.sql and database2.sql

If you try to restore them on a different server, we must pay attention to the restore order, let's say we are starting with empty schemas database1 and database2

This will work:

mysql -u root database1 &lt; database1.sql
mysql -u root database2 &lt; database2.sql


But this will fail:

mysql -u root -p database2 &lt; database2.sql
mysql -u root -p database1 &lt; database1.sql


Because the database2.myview references a table that does not exist.

TLDR: if you are running database restores in parallel and there are references between them you could get into trouble.