Does Kafka DSL context.forward() ensures delivery?

Question

I'm writing my custom KStream transformer and I want to store certain records to state store and later (from punctuate) resend them.
Yet I don't want to keep them in state store - and I have no tombstone in my flow to clean them later from the store - so I want to explicitly clean the records from store after they are forwarded:

   context.forward(key, value)
   store.delete(key)

I'm not sure if the message is not lost when there is failure later in topology.

Does KStream still ensures at-least-once delivery with such usage. For example by:

1. context.forward() returns only after successful processing
2. context.forward() return immediately but record is deleted from store only when all messages from context are processed
3. any other mechanism....