Docs for deletions in Estuary (#1723)

site/docs/reference/deletions.md

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+# Handling Deletions in Estuary Flow
+
+Estuary supports two categories of deletions: **soft deletes** and **hard deletes**. These deletion types determine how documents are marked and treated within the system. Below is an explanation of each category.
+
+## Soft Deletes
+
+Soft deletes occur when a document is marked as deleted but is not physically removed from the destination. Instead, it is flagged for deletion with a specific metadata field.
+
+- **Flagging Soft Deletes**: The field `_meta/op` is set to `'d'` to indicate that a document has been marked for deletion.
+- **Document Retention**: The document remains in the destination even though it is marked as deleted.
+- **Filtering Soft Deleted Documents**: To exclude soft-deleted documents from queries, you can filter out documents where `_meta/op = 'd'`. This ensures that soft-deleted documents are ignored without permanently removing them.
+
+## Hard Deletes
+
+Hard deletes go a step further than soft deletes by permanently removing documents from the destination.
+
+- **Flagging Hard Deletes**: Similar to soft deletes, the `_meta/op` field is set to `'d'` for documents that need to be deleted.
+- **Document Removal**: Once a document is flagged, a query is issued to physically remove any document marked with `_meta/op = 'd'` from the destination.
+- **Supported Materialization Connectors for Hard Deletes**:
+  - Snowflake
+  - Google BigQuery
+  - Databricks
+  - Amazon Redshift
+  - Elastic
+  - PostgreSQL
+  - MySQL
+  - SQL Server
+  - AlloyDB
+  - MongoDB
+  - MotherDuck
+  - TimescaleDB