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+**MD file:** `Data Contract.md`  
+**Estimated reading time:** 11–13 minutes
+
+# Data Contract
+
+## Definition
+
+A **Data Contract** is an explicit agreement between a data producer and data consumers about the structure, meaning, quality, and reliability of shared data.
+
+## Simple Mental Model
+
+> **A Data Contract is an API contract for data.**
+
+A producer should not unexpectedly change data that downstream consumers rely on.
+
+## How It Works
+
+A contract might specify:
+
+```text
+Dataset: Viewing Events
+Owner: Streaming Platform
+
+Required fields:
+event_id: string
+content_id: string
+event_time: timestamp
+watch_time_ms: integer
+platform: string
+
+Freshness:
+Available within 15 minutes
+
+Quality:
+event_id must be unique
+content_id NULL rate < 0.5%
+
+Breaking changes:
+60-day notice required
+```
+
+## Example
+
+Without a contract:
+
+```text
+watch_time_ms renamed
+↓
+Pipeline breaks
+↓
+Gold stops updating
+↓
+Executive dashboard stale
+```
+
+With a contract:
+
+```text
+Proposed breaking change
+↓
+Consumers notified
+↓
+[[Impact Analysis]]
+↓
+Migration planned
+↓
+Consumers migrate
+↓
+Old field removed
+```
+
+## How It Fits Into the Bigger Picture
+
+Contracts can define [[Metadata]], expected [[Data Quality]], ownership, and change rules.
+
+[[Data Lineage]] shows who depends on the contract.
+
+## My Company / Real-World Context
+
+If analytics depends on external fields such as `content_id`, `watch_time`, `device`, and `event_time`, important assumptions should be explicit in vendor or internal integration agreements.
+
+## CTO Perspective
+
+Data Contracts are about managing dependencies and accountability.
+
+Ask:
+
+> **What are downstream teams allowed to rely on, and how do producers communicate breaking changes?**
+
+Use stronger contracts where data is critical, highly reused, cross-team, or vendor-controlled.
+
+### Questions to Ask
+
+- Who produces this data?
+- Who consumes it?
+- What fields and semantics are guaranteed?
+- What quality and freshness are expected?
+- What counts as a breaking change?
+- How much notice is required?
+- Can [[Data Lineage]] identify affected consumers?
+- Who approves contract changes?
+
+## Meeting Scenario
+
+**Situation:** An internal application team wants to rename analytics fields during a release.
+
+**Possible response:**
+
+> "Before changing the fields, let's identify downstream dependencies and treat this as a data-interface change. We need to agree on the new contract, provide a migration period, and verify affected metrics and reports before removing the old fields."
+
+## Key Takeaways
+
+- A Data Contract defines expectations between producers and consumers.
+- It can cover schema, meaning, freshness, quality, ownership, and change management.
+- Contracts reduce unexpected downstream breakage.
+- [[Data Lineage]] helps identify affected consumers.
+- Treat important shared data interfaces with similar discipline to APIs.
+
+## Related Concepts
+
+- [[Data Lineage]]
+- [[Data Quality]]
+- [[Metadata]]
+- [[Data Governance]]
+- [[Impact Analysis]]
+- [[Data Observability]]
+- [[Schema Evolution]]
+- [[API Contract]]