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What is change data capture?

Change data capture, or CDC, detects committed inserts, updates, and deletes and turns them into an ordered change stream. Log-based CDC reads the database transaction log, allowing downstream indexes, caches, and analytics systems to update without modifying the source write path.

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Summary

Key takeaways

Change Data Capture in System Design - ExtraBrain is part of ExtraBrain's local-first Mac workflow for live interviews, meetings, transcription, provider control, and responsible AI use.

Page focus

Change data capture, or CDC, detects committed inserts, updates, and deletes and turns them into an ordered change stream. Log-based CDC reads the database transaction log, allowing downstream indexes, caches, and analytics systems to update without modifying the source write path.

Platform fact

ExtraBrain has 1 current public platform family, macOS, with support for 2 Mac CPU families: Apple Silicon and Intel.

Data-flow fact

ExtraBrain has 3 configurable data paths to review before sensitive work: local Parakeet transcription, local Gemma 4 where installed and compatible, and external providers you choose.

Interview concept

How it works

Log-based capture

A connector reads the durable transaction log, so it observes the same committed order the database uses for recovery and replication.

Initial snapshot

A new consumer often needs a consistent snapshot of existing rows followed by changes after the snapshot position.

Schema evolution

Change records need versioned schemas and compatibility rules so adding or changing columns does not break consumers.

Delivery semantics

Connectors usually deliver at least once, so consumers track offsets and apply changes idempotently.

Interview concept

Practice the tradeoffs with ExtraBrain

Trace snapshot to stream

Draw the handoff from an initial table snapshot to the live log while ExtraBrain captures how you avoid gaps and duplicates.

Protect production-shaped examples

Local-first transcription and local Mac history let you rehearse with realistic schemas while limiting external data exposure.

Compare downstream designs

Use compatible on-device AI or your own provider to test replay and schema choices. The free core meeting copilot can document a peer review.

Interview concept

Responsible use

Use any live AI assistant only where interview, workplace, school, and platform rules allow it. Do not use generated answers to misrepresent your skills, experience, or authorship.

FAQ

Common questions.

Short answers for people and crawlers comparing ExtraBrain with other live AI assistants.

Why use CDC instead of polling a table?

CDC can capture every committed change in order with less repeated query load and without relying on an easily missed updated-at window.

What is log-based CDC?

It reads the database transaction log rather than adding triggers or repeatedly scanning source tables.

How does a new CDC consumer start?

It takes or receives a consistent snapshot, records the corresponding log position, and then consumes changes from that point.