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Design Messaging With Message Deletion

DatabricksSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteSystem Design

Last updated

Design real-time messaging with conversations, history, and deletion that converges across storage layers and online or offline clients. Clarify authorization and retention, then address duplicate events, edit/reaction races, search and attachment cleanup, reconnect behavior, regional failover, audits, and strict erasure.

Design a real-time messaging application with channels or conversations, message history, and message deletion. Focus especially on how deletion behaves across storage, caches, search, connected clients, and offline clients.

Constraints & Assumptions

  • Messages have stable IDs and belong to one conversation.
  • Clients may reconnect after being offline and may receive duplicate events.
  • A deletion must preserve enough information for clients to converge without exposing deleted content.
  • The exact retention, legal, and authorization policy is not prescribed; ask before selecting hard versus soft deletion.

Clarifying Questions to Ask

  • Who may delete a message, and is there a time limit?
  • Should replies, reactions, and attachments remain?
  • Is deletion reversible or auditable?
  • Must search removal be immediate?
  • What should an offline client display when it reconnects?

Follow-up questions

  • Support deletion of an entire conversation.
  • Meet a strict erasure requirement across backups.
  • Preserve ordering during a regional failover.