Sequelize query Performance issues with associations

[empty boats]

I'm trying to upgrade a Node app from Sequelize v3 to v6 that uses a Mysql db. The queries involving model associations/relationships are much slower on v5/v6 than they are on v3/v4. It almost seems like Sequelize isn't using the table indexes when doing inner or outer joins? Or is there some other change in v5 I'm missing to speed up queries on model relationships? Whether using node 10/12/14 doesn't seem to make a difference. 

[Roye]

Sequelize just builds the queries for you. You can log the queries to see if indexes should be tuned