Currently, inherited from Substrate, if mempool is full, fraud proofs are treated same as any other tx: if a new one is submitted, an old one may be discarded.
Fraud proofs, however, are special and time-sensitive - they should get processed before the challenge period ends. It is important that in times of high demand, the block builder gives priority to older fraud proofs first, which have to be included in a block before new ones are accepted. "Older-younger" order on fraud proofs should be imposed by block height in that domain, not time of arrival.
Currently, inherited from Substrate, if mempool is full, fraud proofs are treated same as any other tx: if a new one is submitted, an old one may be discarded.
Fraud proofs, however, are special and time-sensitive - they should get processed before the challenge period ends. It is important that in times of high demand, the block builder gives priority to older fraud proofs first, which have to be included in a block before new ones are accepted. "Older-younger" order on fraud proofs should be imposed by block height in that domain, not time of arrival.