AWS Lambda in Java Cannot Connect to RDS using password: Access Denied Error for User 'admin'

I've deployed an AWS Lambda function written in Java that needs to connect to an RDS MySQL database. However, I'm encountering an "Access denied for user 'admin'@'172.30.49.57' (using password: YES)" error in the Lambda logs. Here's an overview of my setup and what I've checked so far:

Lambda Configuration:

• Runtime: java17

• Memory: 512 MB

• Timeout: 300 seconds

• VPC Configured with subnets: [Allow IPv6 traffic = false, subnet-01c4a541d35b432d3(Private), subnet-09fb788a99e6a5d3e (Private)] and security groups: [sg-0ca99160443168dba (default), sg-0c1cfc93ecb7f3f4c (rds-rdsproxy-2), sg-052e055d8b9a40bc1 (my-db-sg) | my-db-mysql-security-group , sg-0726e010ca51fb672 (rdsproxy-lambda-2), sg-0fb411f522f101a61 (lambda-rdsproxy-2)]

• Environment Variables: DB credentials and RDS proxy host

RDS Configuration:

• Instance: my-db, Class: db.r5.large, Engine: mysql, Version: 8.0.35
• Publicly Accessible
• Security Groups: rds-rdsproxy-2 (sg-0c1cfc93ecb7f3f4c), my-db-sg (sg-052e055d8b9a40bc1)
• Proxy Endpoint: proxy-XXXXX-my-db.proxy-ckeyagwkfxol.us-east-2.rds.amazonaws.com
• Database authentication: Password authentication

Security Group and Network:

• Verified Lambda and RDS instances are in the same VPC.
• Ensured the security groups allow inbound and outbound traffic between Lambda and RDS. IAM Role:

The Lambda execution role has necessary permissions. I've double-checked the database username, password, and connection string. Everything seems correct, but the connection still fails.

Additionally, the admin user on RDS has extensive permissions, including GRANT OPTION and rights to SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, etc., on all databases, which suggests that permission issues within the MySQL database are unlikely to be causing the access denial.

Has anyone faced a similar issue or can point out what I might be missing? Any help would be greatly appreciated.