stateful-functions | Stateful Functions for Apache Flink | SQL Database library

First question is about state TTL. How can I give to state to TTL? Example says: After 30 days, the “Fraud Count” function will receive an expiration message (from itself) and clear its state. Should I do this manually or is there another feature? How can I do this manual?

You can do this manually using delayed message. In effect, you can create a call back trigger by sending yourself a message on a delay. This message is durable and will not be lost in case of failure. If you look at the fraud count function, in the model serving example, you will see that it does exactly this. When a value is received a ttl message is sent with a 30 day delay. When that message is received the count is decremented.

Second Question about keyedstream. Example says: multiple instances of “Fraud Count” will exist — for example, one per customer account. Should I put values to PersistedTable? For example . Can I clear state to specific key?

All function instances are "keyed", in that user code is always invoked within the scope of a key, and all Persisted fields are scoped to that key. The key is the "id" component of an address. In your example, you could have a function "CustomerFunction" that tracks information on each customer of your buisness. When you want to interact with that customer, you will message it specifying that customers uid as the "id" of the address.