How to get end user's access-key and secret-access-key by using accountId and registered email/username w.r.t "amazon s3" in spring boot application ?

Once the secret key is generated, it cannot be retrieved. The ListAccessKeys (https://docs.aws.amazon.com/IAM/latest/APIReference/API_ListAccessKeys.html ) documentation emphasizes that for AWS account security, the secret access key is only available during key and user creation.

To address your issue, consider other solutions, for example implementing federated login alternatives

Good Luck!