Cost effective stack.
1. DynamoDB for database
2. Lambda / Vercel for backend
3. Netlify / Vercel / Surge / Render for frontend
4. S3 for file/image hosting
5. Cloudinary for image hosting
6. IFTTT to webhook for cron
7. RedisLabs for queues, cache
8. Figma for designing and prototyping
9. Porkbun for $6 .com domains
10. Cloudflare for DNS
11. Clubhouse for project management
12. AWS Activate for up to $100k in AWS Credits
This setup is enough to handle ~1M/requests a month, more or less, depending on the application.
If you are getting more traffic than that, your startup will be making money, so you won't mind upgrading. :)