PingPay — Pay Per Call APIs on Rootstock

Hi, I’m Carol, Developer Program Manager at Rootstock. When a hackathon wraps up, I love catching up with the prize winners to learn what they built, how they pulled it off, and where they hope to take it next. Fresh from ETH Global Prague 2025, I sat down with solo hacker Kadir Metehan, the creator of PingPay, a payment tool that lets developers pay for API usage one call at a time using Rootstock-based stablecoins. Here’s the story behind the project, the sprint that produced it, and Metehan’s roadmap for growing PingPay.

Meet Metehan and PumpFlow

Metehan [LinkedIn: www.linkedin.com/in/metehançalışkan / X: https://x.com/kmetehanclskn] earned his degree in Electrical & Electronics Engineering from Bilkent University. He is now a co-founder of PumpFlow, a meme token launchpad that has crossed 20k unique users in five months and processed $1.3 million in volume within three months. Those results gave Metehan the confidence to enter Prague’s in-person hackathon on his own and push himself to ship something new in just a day.

Introducing PingPay — Pay As You Go for APIs

Most developers still pay for infrastructure through a monthly subscription, even when their usage is unpredictable. PingPay flips that model by letting builders pay for each individual API request with stablecoins such as rUSD or USDC held in MetaMask. The design draws on Coinbase’s X 402 standard, adapting it for the Rootstock network so payments are clear on chain and developers avoid overbuying capacity they never use.

Check the project details here:

• https://github.com/metehancaliskan/PingPay

• https://ethglobal.com/showcase/pingpay-vdknr

From Idea to Demo in a Day

Metehan spoke with the Rootstock team on day one, scoped his idea, and then coded through a single 24-hour window to have PingPay ready for judging. Time was so tight he had to leave early for a flight, missing the final showcase, but the judges still selected PingPay as one of the ETH Global Prague 2025 winners.

Building on Rootstock for the First Time

PingPay was Metehan’s first Rootstock build, yet his EVM background meant he could drop in Solidity code without reading additional docs. “EVM compatibility meant I could just write the contracts the way I always do,” he told me. The main hiccup was tooling as he struggled to locate a USDC liquidity pool and wound up using Blockscout because other explorers didn’t surface the data he needed. Still, once the contracts were deployed, transactions behaved exactly as on other EVM chains.

What Comes Next

Metehan envisions an SDK that any Rootstock developer can import with a single line, instantly enabling pay-per-call billing inside their dApps. He’s mapping out a two-month development schedule followed by a marketing push (Telegram community included) and is already preparing a milestone plan to apply for a Rootstock Collective grant.

Final Thoughts

PingPay shows how a solo developer can marry open standards like X 402 with Rootstock’s EVM environment to create practical tooling in a single weekend. By turning fixed-fee API subscriptions into lightweight per-call payments, Metehan lowers barriers for both new projects and established teams looking to trim costs. We’re excited to see the SDK take shape and to follow PingPay’s journey from hackathon demo to production infrastructure for the Rootstock community.

Get Involved

Ready to start building on Rootstock? Here’s how you can get involved today:

📖 Explore the Docs – Get started with Rootstock development.

🏆 Check out the Hacker Hub – Learn about past hackathons and upcoming opportunities.

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💬 Join the Community – Connect with other builders on Discord.