Just seems like a lot of extra fiddly stuff to go wrong for monolithic apps. I get it if you have went all in on microservices as each "client" request can fan

Just seems like a lot of extra fiddly stuff to go wrong for monolithic apps. I get it if you have went all in on microservices as each "client" request can fan out to hundreds of requests, each requiring an auth check. But still, I'm not sure that I've seen an auth/roles database that couldn't fit (at least) the important stuff itself in RAM itself fwiw. Even 1TB of RAM is relatively affordable (if you are not on the hyperscalers) and you could fit billions of users in that, which at least in theory means you can just check everything and not have another store to worry about.