Latest / The Indie Hacker Podcast with Fexingo: Solo Developers, SaaS Side Projects, and Independent Tech / How a Solo Dev Built a SaaS That Sells Only via Cold Email
Transcript
- Lucas: So this is a story about a solo dev who did something most indie hackers would tell you is impossible: he built a SaaS that hit 10K in monthly recurring revenue without a single blog post, without a Product Hunt launch, without any social media presence at all. Luna: Wait — no marketing at all? How do people even find out the product exists? Lucas: They don't find it. He finds them. His entire growth channel is cold email. And I know what you're thinking — cold email feels like spam, it's annoying, nobody opens those messages. But he had a 40 percent open rate and a 15 percent reply rate. That's better than most newsletter open rates. Luna: Okay, I need to hear the specifics. What is the product, and how did he get those numbers? Lucas: The product is a simple API monitoring tool. Think of it as a lightweight alternative to something like Pingdom or UptimeRobot, but specifically designed for developers who need to monitor custom API endpoints and get alerts via Slack. He built it because he was freelancing and kept getting paged for API failures that his existing tools didn't catch. Luna: So he built for himself first. Classic indie hacker origin story. Lucas: Exactly. But here's where it gets interesting. Once he had a working product, he didn't announce it anywhere. No Hacker News post, no Twitter thread. Instead, he spent a weekend scraping every public directory of developer tools and APIs he could find — things like the ProgrammableWeb API directory, GitHub topics, even the Shopify app store. He compiled a list of companies that were already using APIs but didn't have a dedicated monitoring tool. Luna: That's smart. He's finding people who already have the problem but aren't actively looking for a solution because they don't know the tool exists. Lucas: Right. And the key was that his emails were incredibly short. Three sentences. First sentence: 'I noticed your company uses the Stripe API and the Twilio API.' Second sentence: 'I built a tool that monitors those endpoints and alerts your team if they go down.' Third sentence: 'Would you be open to a five-minute call to see if it's useful?' That's it. No link, no demo, no case study. Luna: No link? That's counterintuitive. Usually you want to drive people to a landing page. Lucas: He told me he deliberately left out the link because he wanted the reply, not the click. If they replied, he knew they were genuinely interested. Then he'd send a personalized Calendly link. That way, his open rate and reply rate weren't diluted by people who just clicked out of curiosity and never converted. Luna: That makes sense. But still — a 40 percent open rate on cold email? How did he avoid the spam folder? Lucas: He used a dedicated sending domain, not his main one. He warmed it up over two weeks by sending a few emails a day to his own accounts and replying. And he never sent more than 30 emails per day. He was targeting very specific companies, so the volume was naturally low. He also personalized each email with the actual company name and the APIs they used — no merge tags gone wrong. Luna: So it's almost like a concierge sales process. Manually finding leads, manually writing emails, manually booking calls. Lucas: Exactly. And that's why it worked. He wasn't blasting 10,000 emails. He sent maybe 500 emails over three months. Out of those, he got around 75 replies, booked 30 calls, and converted 12 into paying customers at $50 per month. That's 600 dollars in MRR from the first batch. But then those customers started referring others, and he added another 8 customers through word of mouth. Within six months, he was at $1,200 MRR. Luna: And he got to 10K MRR just from referrals after that? Lucas: Not exactly. He kept doing cold email in parallel, but he also added a very simple referral program: existing customers got one month free for every new customer they referred. No dashboard, no fancy tracking — just a unique email alias for each customer. He'd manually check if the referral came through. That accounted for about 30 percent of his growth. The rest was continuing the cold email process, but now he had social proof: he could mention that companies like Zapier and Airtable were using the tool. Luna: Speaking of which — a quick honest thing. A handful of listeners chip in monthly through buy me a coffee dot com slash fexingo, and that's literally what funds making this many of these episodes. So if today's conversation gave you something usable, that's the reason it's ad-free and stays that way. Lucas: Yeah. And it's not a big ask — just that it's listener-supported, and that's how we keep doing deep dives like this without any sponsor pressure. Luna: Exactly. Back to the cold email story — what was the biggest mistake he made early on? Lucas: He initially tried to include a case study PDF attachment. Open rates dropped by half. People don't trust attachments from strangers. Once he removed that, his open rates went back up. The other mistake was emailing on Monday mornings. He found that Tuesday and Thursday afternoons got the best response rates — maybe because people are less overwhelmed. Luna: So the lesson is: keep it human, keep it small, and test everything. Lucas: Exactly. And the bigger takeaway is that for very niche B2B developer tools, cold email might actually be more effective than content marketing. Because the audience is small and the pain point is specific. Writing a blog post that ranks for 'API monitoring tool' might take months to get traction. But sending 30 personalized emails can get you a customer in a week. Luna: But doesn't this only work if you're selling to technical founders or engineers? Like, if you're selling to a non-technical manager, cold email probably won't work. Lucas: That's a great point. The tool is for developers, and developers are used to getting cold emails about tools. They're actually more receptive if the email is relevant. But if you're selling HR software or something to CFOs, this approach might not work because those people get spammed all day. The key is to pick a niche where cold outreach is still novel and appreciated. Luna: So what's next for this founder? Is he scaling the cold email or trying other channels? Lucas: He's actually scaling very cautiously. He hired a part-time assistant to help with lead research, but he still writes every email himself. He's at 10K MRR now and he's happy with that. He doesn't want to turn it into a big company. He's a solo dev who wants to keep it that way. Luna: That's the dream, honestly. A sustainable lifestyle business that doesn't require constant growth. Lucas: Yeah. And it proves that you don't need to be loud online to build a successful SaaS. You just need to find the right people and talk to them directly. Luna: Alright, that's a wrap on episode 98. For those who want to check out the tool, we'll link it in the show notes. And if you found this useful, consider supporting us at buy me a coffee dot com slash fexingo. Lucas: See you next time.