Skippr Docs

Appearance

What MongoDB CDC Capture Shape Looks Like ​

May 2026

MongoDB CDC capture shape is the change stream. Updates are important because Skippr asks for the full document after image, not just a patch fragment.

Short Answer ​

MongoDB CDC capture shape in Skippr is the MongoDB change stream backed by the oplog. The supported captured operations are insert, update, and delete. For updates, the docs specify fullDocument: updateLookup, which means Skippr uses the full document after image rather than relying on a partial patch alone.

A concrete example makes that clearer. If document { _id: 42, status: "placed" } changes to { _id: 42, status: "shipped" }, the useful capture shape for a warehouse is the full updated document keyed by the same logical identifier. That is much easier to reconcile than a partial update fragment with no after image.

Why Teams Struggle with This ​

MongoDB updates can be misunderstood if you approach them like row updates from a relational log. The docs are explicit that change streams are the capture source and that updates are paired with a full-document lookup for the after image.

  • Change streams require MongoDB to run as a replica set or sharded cluster.
  • The source of truth for CDC is the change stream backed by the oplog, not periodic collection scans.
  • Updates are captured with a full after image via fullDocument: updateLookup.
  • The public docs describe mutation kinds and resume behavior, but they do not publish a larger custom event schema beyond that.

How Skippr Handles It ​

Skippr makes MongoDB CDC easier to reason about because it stays faithful to the supported source mechanics. The change stream is the event source, the resume token is the restart cursor, and the update after image is made explicit in the docs.

That is especially helpful for warehouse use cases. Once the update is captured as a full document after image, reconciling the document into a final-state row becomes much more direct.

  • MongoDB CDC uses change streams backed by the oplog.
  • Supported operations are insert, update, and delete.
  • Updates use fullDocument: updateLookup to retrieve the full after image.
  • The same CDC path can feed destinations that reconcile to exactly-once final state.

What the First Useful Version Looks Like ​

The key insight is that MongoDB CDC is not just a list of events. It is a document mutation stream with enough context to rebuild the current document state for a given key.

That is why the full-document after image matters so much.