If you are migrating to AWS RDS, I recommend AWS Data Migration service. I migrated my live database (~50GB) from Mysql to Postgres (both RDS) with zero downtim

If you are migrating to AWS RDS, I recommend AWS Data Migration service. I migrated my live database (~50GB) from Mysql to Postgres (both RDS) with zero downtime. I used AWS Schema Conversion Tool for initial PG schema. I customized the generated schema for my specific needs.