I've been working on my main SaaS for over 2 years now and brought it to $16k MRR. Along the way, I've always been tinkering with other ideas and side projects.
I've tried a lot of things:
All of them flopped, but I built them mostly for the experience.
Recently, I started working on a new product, an email marketing tool for SaaS founders. All those learnings helped me build a full-featured app with a reliable backend and AWS integration in about 2 weeks (while still running my other startup).
Here's what I've learned:
Two non-negotiables
Get the foundations right
The most important thing is nailing your architecture early. When you have a solid foundation - properly typed database, coherent structure - iterating on features becomes 10x easier.
Here's what I recommend:
Why does all this matter? When you have proper types end-to-end, it's 10x easier for AI to understand all the relationships in your codebase.
My take on testing
I strongly believe you should have unit tests for all your core functionality. Mock your database using something like PGlite and you're good to go.
This helps you move fast while making sure your app actually works. Most of your endpoints should be \~5 lines where you just call a well-tested function.
As for UI tests and E2E tests - I don't think they help at this stage. They slow you down, and you'll be changing your UI constantly. If you want to iterate quickly, skip them for now.
One more tip: keep configuration in code
Whenever you can, avoid manual setup. If you need to do something on AWS or GCP, use Terraform. Don't go through dashboard hell manually clicking around. It'll speed you up massively in the long run.
Writing the code
Run a few agents in parallel. Once you already have the schema, it's easy to add different API requests, screens, etc. at the same time.
Every 4–6 hours, stop and review everything you've done. Use Cursor Review, ask Claude Code to give you feedback about your PR, and verify that it added zero unexpected fields in the database. Make sure the flow still works as expected.
Don't allow AI to write code for days without review - it'll be incredibly hard to clean up and make useful.
That's the flow. If you're building a SaaS and need to set up email sequences for onboarding or retention, check out Sequenzy - we have a generous free tier and you can start sending sequences within minutes of signing up.
Good luck, and ship fast!