End-to-end encryption, or E2EE, is a system of communication that encrypts messages for everyone including the messaging service except the user receiving the message and the user that sent the message.
From version 4.2 on, MongoDB introduced E2EE Field-Level Encryption (FLE) to encrypt user data during transit and only decrypt the data on the client-side.
MySQL ensures E2EE by encrypting the connections between the server and the client through the Transport Layer Security (TLS) protocol.
PostgreSQL ensures that communication across a network is SSL-encrypted or GSSAPI-encrypted.