No, this is just say a list of messages, not that much of data. We tried to move to pg-native, but it didn't help. Problem was in Sequelize. But in my internal tests even Sequelize was the fastest library on the market.

Looks like you’re blaming Postgres for Something that sounds like Sequelize’s fault. You should try prototyping parts of your application in a language that is better supported. Last I used Sequelize I was disappointed at how poorly it fared compared to other libraries like Django ORM or SQLAlchemy.