All Notes

Data Models

Database

Early database systems modeled data as a hierarchy of records

Hierarchical Data Model

Long-running queries need a consistent snapshot of the database

Snapshot Isolation
Database Snapshot

Event Sourcing works on the same principle as Snapshot Isolation

Event Sourcing
Snapshot Isolation

Reads don't need locks in Snapshot Isolation mode

Snapshot Isolation
Transactions

Read Models can provide snapshots of the application state at a point in time

Read Model
Event Sourcing

Denormalization does not eliminate the need for transactions

Read Model
Denormalization

Read Models are best kept schemaless

CQRS
Read Model
Schemaless
Document Data Model

Read Models store ready-to-ship information

CQRS
Read Model
Apache Avro
JSON

Read Skew is acceptable only during application runtime

Read Committed Isolation
Non-repeatable Reads
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