How to get latest 100 event logs only from Smart Contract using web3?

Question

I deployed my smart contract to the network and building frontend which will interact with the smart contract. The problem is when I get the event logs using web3.contract.getPastEvents(), it returns all the events that is occurred so far. My smart contract emits lots of events a day, so one year later, there will be so many event logs saved, and this means the getPastEvents() function would return big data. However, I only need 100 latest events. This is my current code which returns all events.

const events = await factory.getPastEvents('allEvents', {
        filter: { from: account },
        fromBlock: 0,
        toBlock: 'latest'
});

How can filter 100 latest events only? Of course, I can filter using block number but I can't ensure how many blocks would contain exactly 100 events. Any solution?

Answer 1

You cannot directly get the past 100 events because web3 does not know how many events there are in each blocks before checking them.

However, you could achieve that indirectly by getting the past Events of the last, say, 100 blocks. If there are less than 100 events in the result, check the 100 previous blocks and add those events to the first result. Then iterate over past blocks in that way until you have 100 events in your list.