Interesting, looking at the history it appears to be a spotty last few months. "Major" outages every two weeks or so. I wonder what brings instability into such a mature product.
Pre-acquisition WhatsApp was built using Erlang and had an impressively large user-to-server ratio IIRC. I expect that since then things have mostly been rebuilt to use existing meta shared infrastructure which might not be as stable or efficient.
downdetector.com is also showing a spike of users reporting issues with Instagram around the same time. Assuming both products are hosted with the same infra, perhaps the issue is up-the-chain and not related to any changes in the product per se.
