Succeed in a SQL interview
Hi Leon – congrats on reaching $7k MRR! Looks like a great tool to practice SQL – I'm curious how did you come up with the idea?
I have been working in the data science and machine learning space for over 10 years.
In the last few years, I built an applied machine learning & data science team at Apple from scratch.
As a senior manager, I interviewed and hired many people, including young professionals, interns, and college graduates.
And I've noticed that there is a very strong correlation between hands-on data processing skills (e.g., using SQL to extract data) and new hires' productivity and work performance.
SQL is pretty much a must-know language for any data analytics professional, so during Covid, I launched a SQL video course.
My goal was to teach people from basic SQL syntax to advanced window functions in a business context and help college graduates master SQL, ace their job interviews, and excel at their new jobs.
Soon after I launched the SQL course, I realized I needed a place for students to practice SQL assignments and coding problems, and I couldn't find an interactive SQL playground service online, so I created my own SQL playground and hosted it on
So the tool started out from your video course – it was probably a good way to test the product in real life on your students. But how did you find your first paying customers outside of that?
A lot of hustling, trial and error, but I got my first 100 customers (mostly free tiers) by visiting forums such as Reddit or Quora, answering SQL-related questions, and organically mentioning
if I see there is a fit.
So after over two months of marketing and improving the product, I finally got my first paid customer.
When I received the automated email receipt, it was beyond exhilarating.
Is there still a lot of manual work to find customers, or you've been able to take this to a point where clients find you organically?
Nowadays, most customers come from organic Google searches and word of mouth.
The rest of the traffic came from a forum such as Reddit.
I don't spend much time on Reddit now, as I've developed an automated machine learning model that helped me identify interesting questions and potential leads and notify me so I can log in and respond to them.
What's your advice for other microfounders who want to get started?
1. Just go ahead and do it. Launch your MVP first.
Reid Hoffman famously said that if you are not embarrassed by your first version, you launch too late.
2. Don't overthink/overengineering your product before seeing any tractions.
There is no need to think about scaling up your offerings to thousands of people before landing your first 10 paid customers. Those issues didn't exist yet.
3. Talking to customers and understanding their problems are important but don't listen to every customer, especially those who never paid for your service.
As a solo/micro founder, you have to prioritize your daily task and product features ruthlessly, so you must focus on things that help you sell and create value for your customers.
Feedback from free tier users is usually not very helpful. Even if you agree to add features they ask for, they always come up with other excuses not to pay for your product.
Instead, I launched a private slack channel for my paid customers.
They can ask me any SQL questions, and in return, I often get great feedback from them.
When prioritizing product features, I'd often prioritize ones that came from customers directly rather than something that came up from myself.
4. It may take a long time to find the first paid customer, so if you believe your idea and have faith, be patient and spend more time marketing your product as soon as possible.
I love how you say that you need to believe in your idea and have faith. I think this is one of the most important things when building microstartups.
Did you have your own moments of doubt? If so, how did you overcome them?
Great question, I doubted my idea constantly, especially in the beginning, when no one paid for @sqlpad. I tried to not focusing on worrying too much but on how to find new customers. E.g, kept answering questions on Reddit and organically mention @sqlpad when there was a fit.
Founded: Jun 2020
Age: 3y 3m
Startups to $5k MRR