My one-person SaaS architecture with over 250k users:<p>* Flask + Flask-Login + Flask-SQLAlchemy [1]<p>* uWSGI app servers [2]<p>* Nginx web servers [3]<p>* Dramatiq/Celery with RabbitMQ for background tasks<p>* Combination of Postgres, S3, and DigitalOcean Spaces for storing customer data [4]<p>* SSDB (disk-based Redis) for caching, global locks, rate limiting, queues and counters used in application logic, etc [5]<p>I like how OP shows the service providers he uses, and why he decides not to self-host those parts of his infra. Also, there's a large up front cost involved for any stack (Rails, Django, k8s). I'd be interested in a more detailed writeup with configs, to try out OP's auto-scaling setup. My configs are linked in the gist below [2] for my non-auto-scaling Flask setup.<p>I spend about $4,000/mo on infra costs. S3 is $400/mo, Mailgun $600/mo, and DigitalOcean is $3,000/mo. Our scale/server load might be different, but I'm still interested in what the costs would be with your setup.<p>[1] <a href="https://wakatime.com/blog/33-flask-part-2-building-a-restful-api" rel="nofollow">https://wakatime.com/blog/33-flask-part-2-building-a-restful...</a><p>[2] <a href="https://gist.github.com/alanhamlett/ac34e683efec731990a75ab69d5699a1" rel="nofollow">https://gist.github.com/alanhamlett/ac34e683efec731990a75ab6...</a><p>[3] <a href="https://wakatime.com/blog/23-how-to-scale-ssl-with-haproxy-and-nginx" rel="nofollow">https://wakatime.com/blog/23-how-to-scale-ssl-with-haproxy-a...</a><p>[4] <a href="https://wakatime.com/blog/46-latency-of-digitalocean-spaces-vs-aws-s3" rel="nofollow">https://wakatime.com/blog/46-latency-of-digitalocean-spaces-...</a><p>[5] <a href="https://wakatime.com/blog/45-using-a-diskbased-redis-clone-to-reduce-aws-s3-bill" rel="nofollow">https://wakatime.com/blog/45-using-a-diskbased-redis-clone-t...</a>