Hello Khanh Tran Nguyen,

Basically, a fast growing entity is an entity that grows too fast very quickly, meaning, too many records are created in a short amount of time. 

However there is no such this as "too large" or "too fast". Databases can grow to the maximum file sizes allowed by operation systems. But, as everything in life, it might have some performance impacts. 

So, there are some performance best practices like the ones described in here that might help you to mitigate problems like this one: 

https://success.outsystems.com/documentation/best_practices/performance_and_monitoring/performance_best_practices_data_model/

In resume, as possible, adopt performance methods like: 

• Index your Entities.
• Isolate large Text and Binary Data in another entity.
• Beware of Large Excel Files Performance.
• Make good use of the Delete Rules in Entities.
• Archive old data in separate Entities.

You might also check the following links: 

• https://success.outsystems.com/documentation/11/developing_an_application/use_data/data_modeling/entities/
• https://success.outsystems.com/documentation/11/developing_an_application/use_data/data_modeling/create_an_entity_to_persist_data/
• https://success.outsystems.com/documentation/11/setup_and_maintain_your_outsystems_infrastructure/setting_up_outsystems/possible_setups_for_an_outsystems_infrastructure/high_availability_and_scalability_strategies/
• https://www.outsystems.com/forums/discussion/52534/what-happens-to-large-entities/

Best regards, 

Ana

An g that has a great quantity of records being created every day. The volume of data grows up quickly.

regards

Graça