- WAL: Write-Ahead Logging. A log written in advance. A method of recording changes in a log before actually modifying the DB data
- CDC: Change Data Capture. Detecting in real time what data changed in a DB and passing it to another system.
- CDC can use several methods. One of them is log-based CDC, and WAL is a way of recording that log. Other methods include trigger-based (recording change events with DB triggers), query/polling (querying the DB periodically), and application-level (the application publishes an event at the same time as the change).
- WAL's original purposes include crash recovery, durability, and replication (replicating the data from one DB to another DB), but it can also be used for CDC
- WAL is written in a low-level language understood by the DB engine => Logical Decoding is needed to decode it into a form readable like SQL statements. In other words, WAL -> Logical Decoding -> CDC
Learnings
Small lessons captured before they become long-form writing
2026
- Accessibility can be addressed in PDFs, too.
- You can earn the GitHub startstruck badge by receiving at least 16 stars on a single repository.
- CDC: Change Data Capture. A technology that detects and captures data changes in a database and transmits those changes
- MVVM
- Model: Does this have meaning even without a UI?
- View: Is this a decision about how to represent state?
- ViewModel: Does this transform the Model and state into the behavior of Presentation State that the View can consume?
- MVVM
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- RPC: Remote Procedure Call. A way to abstract communication between a client and a server so it can be invoked like a function. An abstraction for "How do we call a function on another computer?"
- ORM: Object-Relational Mapping. A way to abstract communication between a server and a database so it can be manipulated like objects. An abstraction for "How do we work with a database as objects?"