How to Make Slow Mongo Query on Compound Index with $gte and $lte Fast

I have a mongo collection of IpRanges, with start_address and end_address. I'd like to query given an IP. with compound index on {start_address:1, end_address:1}, this however is still very slow:

db.ip_blocks.find({start_address: {$lte: 1665637698}, end_address: {$gte: 1665637698}})


with .explain(), it appeared that this query causes a lot of scanning and slow, as only the $lte query worked hard, and the second query is scanning what's remaining from the first query.

Here is a trick to speed this up if you are only trying to get the first match:

db.ip_blocks.find({start_address: {$lte: 1665637698}, end_address: {$gte: 1665637698}}).limit(1)

This doesn't cause scan.

However, if you are expecting more than one match, limit(2) or above will cause a full scan.

So to make it work for multiple matches, here is the second trick:

Add this index:

{start_address:-1, end_address:1}

Query with a $maxScan parameter:
db.ip_blocks.find({start_address:{$lte: 1665637698}, end_address:{$gte: 1665637698}})._addSpecial("$maxScan", 100)

As the addresses are ordered in a way helping us to scan, the correct records can be retrieved and also with limited scanning and thus it becomes fast.