Why there is block reorg? When reorg happen?

[leo-xinwang]

For event log indexer, the reorg needs to be handled carefully otherwise events will be missing.

[boundless-forest]

Chain reorgs are quite normal, it depends on many factors, including the network status of the validators, consensus mechanism, and the network latency. We can't predict the chain reorg, but we can handle it properly. The best practice is for indexers to handle reorg situations and correct data promptly. It is recommended to use the third party dedicated indexers instead of writing by yourself, such as Thegraph, as they have well-integrated reorg mechanisms.