pub const MAX_CHECKPOINT_HEIGHT_GAP: usize = 400;
We limit the maximum number of blocks in each checkpoint. Each block uses a constant amount of memory for the supporting data structures and futures.
We choose a checkpoint gap that allows us to verify one checkpoint for
FindBlocks response size is 500 hashes.
1 hash to verify the tip, and discards 1-2 hashes to work around
bugs. So the most efficient gap is slightly less than 500 blocks.