Discordpy: Efficient Invitation Checking

I'm attempting to write a function using the discord.py library. The function is intended to reward a specific user for inviting another user.

The current code I have does indeed work, but I'm worried about the efficiency of the code. Particularly in these two situations:

1. If many users join in quick succession
2. If there are many users in the server (100k+)

My Code:

@client.event
async def on_ready():
    global members_joined
    MAIN_GUILD = client.get_guild() # ID Redacted

    # Get a list of users in the server. This is to prevent additional rewards on leave+rejoin
    invites_before_join = await MAIN_GUILD.invites()
    members_joined = await MAIN_GUILD.fetch_members(limit=None).flatten()

@client.event
async def on_member_join(member):
    global invites_before_join

    invites_after_join = await member.guild.invites()

    for before_invite in invites_before_join:
        for after_invite in invites_after_join:
            if(before_invite.code == after_invite.code and before_invite.uses < after_invite.uses):
                if(member not in members_joined):
                    # code here (redacted)
                    members_joined.append(member) # Add them to the list, so they cannot leave+rejoin to reactivate

    invites_before_join = invites_after_join
    return

As you can see, in my solution I use a nested for loop. I'm wondering if this is something I should be concerned about in terms of efficiency (particularly for the two reasons stated above). The reason I had to do it this way was because I needed the name and ID of the inviter, so I can reward them.

Solution 1:

After being suggested https://github.com/cyrus01337/invites, I took a look and found a more elegant solution using async def on_invite_update(member, invite):

Thank you Lukasz in the comments for the suggestion.