Davydov surveys three approaches to deleting user-related data from an immutable event store: (1) Martin Fowler's reactive approach (not explained in depth); (2) encrypt sensitive payloads per-user and lose the decryption key; (3) compact the affected events out, Kafka-style (acknowledged as 'not a true way'). The Q&A adds a fourth blockchain-industry idea: store payloads separately from events, keep only fingerprints inside events to preserve immutability proofs, and delete the payload on request.