Add a field without breaking consumers

I added a field to an event my service publishes, and three days later a teammate found out a downstream dashboard had silently stopped updating.

Intermediate to advancedRead 6 minDoing: a day7 steps

▶ Start

What you'll have at the end

A new optional field added to your event, with every registered consumer still reading it correctly and a check in place that catches the next one before it ships

Before you start

You need

A service that already publishes an event other services consume, with at least one of those consumers already validating it strictly in production.

Not covered

Removing, renaming, or changing the type of an existing field: those need a new event version and a migration window, not the tolerant-reader fix this recipe covers.

Leans on

7 steps

Where to go next

Give a poison message its own dead-letter queue

if the same message keeps getting rejected on retry after retry rather than failing once on a genuine shape mismatch, that's the poison-message problem to fix instead.

Checked 19 Aug 2026

Part of the Message Queues cookbook