I love sites that offer either functional guests or fast non-email signups, but I don't know how to prevent someone from creating fake accounts and making the matchmaking awful besides rate limiting, but as the expected pool of legitimate players is small, any trivial amount of fake accounts (10s) can severely impact the queues.
I know, I know, "0 users" and "just put something out there", but I really enjoy the back-and-forth of the design and implementation, just a bit lost here so any guidance on what to do, but scoped to the small stakes of the project, would be much appreciated.
Having said that, none of this prevents people from creating fake accounts. On our system I can see people regularly signin in with multiple google accounts, with incrementing digits in the name, trying to abuse the free tier. You'll need to build something yourself for that, depending on your risk surface. For us this involves tracking requests across IP addresses, blocking free access from data centre IPs, blocking bots using AWS WAF, analyzing task patterns to spot people who use multiple residential IPs and a bit more.
there are several auth SaaS providers you could look to for inspiration or adoption
tl;dr - clicking a few buttons at prompts is much less effort (and more commonplace) than unam+pword