What is CDC (Change Data Capture)?

Understanding Change Data Capture (CDC)

If you’ve ever tried to keep two different systems in sync — say, a database and an analytics dashboard — you know it’s tricky. Data changes fast, and if you’re constantly copying entire tables just to keep things updated, it gets slow, expensive, and messy.

That’s where Change Data Capture (CDC) comes in.

What is CDC?

CDC is a way to detect and capture only the changes that happen in your database — new records, updates, and deletions — and send them somewhere else in real time (or near real time).

Let’s understand it with an example

Imagine your e-commerce database as a giant store. Every minute or second, someone:

• Places a new order

• Updates their shipping address

• Cancels an order

• Adds stock to a product

If you were to find out these data changes in almost real-time, efficiently, without wasting time and resources, only changes without copying the entire order, address, and product data.

Real-time use of CDC in an e-commerce platform

• Every new order triggers an update in real-time sales dashboards.

• Inventory changes are sent directly to the search and product pages.

• Customer profile edits update CRM and marketing tools instantly.

Why Use CDC?

Think of CDC like a live news feed for your database:

• Faster — You’re not pulling the entire dataset each time.

• Lighter — Less network and storage overhead.

• Timely — Downstream systems get updates almost in real-time.

• Reliable — Fewer chances to miss changes between syncs.

How CDC Works — The Big Picture

Most CDC implementations follow the same pattern:

1. Watch for Changes — This can be done by reading database logs, tracking timestamps, or using built-in database features.

2. Capture the Event — Record details about what changed (insert, update, delete, and the affected rows/columns).

3. Deliver the Change — Send this change to another system (a message queue, data warehouse, or microservice).

Common Ways to Implement CDC

There are several techniques to detect changes:

• Log-based CDC — Reads the database’s transaction log (very efficient, minimal performance impact).

• Trigger-based CDC — Uses database triggers to log changes into another table (easier to set up, but can slow down writes).

• Timestamp-based CDC — Compares timestamps to find new or updated rows (simpler, but can miss deletes or backdated changes).

CDC Tools in the market

• Debezium

• Airbyte

• Hevo, etc

Where Debezium fits in?

Debezium is an open-source change data capture tool. It connects to your source database logs (MySQL binlog, Postgres WAL, etc.), captures all the row-level changes from the logs, and publishes those events to Apache Kafka so that other systems can listen to those changes and react to them.

Benefits of using Debezium (DBZ)

• Log-based CDC connects to the transaction log of the database.

• Capture real-time data changes

• Supports multiple data sources such as MySQL, Postgres, Oracle, MariaDB, SQL Server, etc

• Ready to use in production.

• Fault tolerance — It maintains the position in the transaction log, allowing it to resume from where it left off in case of failure.

• Capture all the changes, including deleted records.

How Debezium works — High-level

• Read transaction logs from the database.

• Parse logs and Capture data changes

• Serialize the changes to a specific schema, like JSON, Avro, etc

• Publish an event to a message queue like Apache Kafka

When You Should Consider CDC?

CDC is a good fit when you need:

• Real-time reporting or analytics

• Search index updates (e.g., Elasticsearch)

• Sync between microservices

• Data migration with minimal downtime

But it might be overkill for:

• Very small datasets

• One-off migrations

• Systems where “eventual consistency” isn’t critical

Summary

In short, CDC is like putting your database on “live broadcast mode”. Instead of asking “What’s changed?” over and over, you get updates the moment something happens — ready to power analytics, sync systems, or trigger workflows.

With tools like Debezium, implementing CDC is easier than ever. The result? Data that’s always fresh, and systems that are always in sync.