Sync was released recently, and - like many apps before it - directed its users to lemmy.world as a ‘default’ instance, so they’ve had an influx of users to contend with.

Also, if you ask for the ‘next page’ of communities via their API, it’ll just keep feeding you the same ones, over and over, even if you ask for Page 1 Billion, so there’s probably some bots, crawlers, front-ends etc thrashing the hell out of it.

I don’t know about DDoS attacks, but while they’re happening, it seems to act a catch-all to blame any problems on.