Ask HN: Tamper-proof non-repudiation records in PostgreSQL and avoid blockchains?

I am developing an HIPAA compliant audit log application. I am expecting about ~4K/min of audit record insertion. And as such one of the key requirements is tamper proof. Short of using a gigantic hammer like http://bigchaindb.com/ how can I ensure tamper proof and non-repudiation using PostgreSQL.?