# event sourcing

###### tags: `eventsourcing`

https://www.youtube.com/watch?v=i2eVTk2Fb40&ab_channel=ADev%27Story

* complete rebuild
* temporal query
* event replay

owing to object state record by log of events,
we can get the object status at any time before now


### snapshot: record the compiled object in the past

### example:

1. git commit

2. good for parallel processing, log only support read, log as immutable when support parallel process

3. problem for only eventual consistency:

### CQRS: command query responsibility segregation

path of writing data different from reading

pros :

1. split read/write make scale each one easier
2. compatible with event driven

cons:

1. complex pattern

used case:
when great amount of unbalance btw read and write