The Build

Mike and Ian sit down with David Buonasera, CTO of Magnite (00:00:00), to unpack what it really takes to build and scale complex systems in ad tech.

Before becoming the CTO of Magnite, David co-founded SpringServe--a bootstrapped, video-native ad server that grew from an internal tool into an acquisition target. He started his career in finance before joining AppNexus as one of its first 18 employees (00:07:30).

The conversation covers two modes of building (00:13:00): greenfield at SpringServe, where David explains the opportunistic founding moment when Facebook shut down LiveRail (00:29:00), and the unification of teams at Magnite (00:53:00).

They dive into a technical breakdown of budget pacing in distributed ad systems (00:16:30), why enforcing a spend cap becomes one of the hardest problems in ad tech (00:25:00), and the emotional reality of going through an acquisition process that doesn't always close.

Also covered: real-time data as a product differentiator (00:44:00), migrating infrastructure without disrupting clients (01:05:00), and the A/B testing pitfalls that trip up even experienced engineering teams (01:12:00).

Key Takeaways

• "Just stop spending at $100" is not a simple problem. In a distributed ad system, no single machine knows the true spend at any moment. Impression data arrives late, routes through different servers, and the feedback loop lags by minutes or hours. Budget overruns are almost never one bug--they're several compounding. The fix is less about clever algorithms and more about instrumenting the full data pipeline so you know exactly where things break down.
• When a critical system is failing, resist the urge to start over. Everyone's first instinct is to declare it beyond repair and rewrite it. That rewrite will take longer than you think, clients will leave before it ships, and you'll introduce new bugs in place of the old ones. Get it stable first, then have the rewrite conversation.
• A/B tests in ad systems can lie to you. Make your ad server faster, run a split test, and the faster side looks like it's printing money. Roll it out globally and the gain evaporates; budgets are finite and pacing algorithms just redistribute spend. Any test where both sides share a budget constraint isn't truly isolated.
• If teams are still on separate Slacks and VPNs, they're still separate companies. Tooling fragmentation is easy to deprioritize because it doesn't feel urgent. But every time an engineer has to switch VPNs to collaborate, it's a reminder that they don't actually work together yet.
• The number on the term sheet isn't the whole story. If the acquirer doesn't understand why they're buying you, the product gets deprioritized regardless of what the check said. And once you hire a banker and go to market, everyone knows you're for sale--which changes the dynamic in ways that don't always help you.

Chapters

• 00:00:00 - Meet Dave Buonasera
• 00:03:30 - Goldman to Ad Tech
• 00:07:30 - Inside Early AppNexus
• 00:13:00 - Democratizing Data Access
• 00:16:30 - Budget Pacing Explained
• 00:25:00 - Fixing Distributed Systems
• 00:29:00 - Building SpringServe
• 00:44:00 - Real-Time Data as a Feature
• 00:53:00 - Merging Cultures at Magnite
• 01:05:00 - Migration Without Client Disruption
• 01:12:00 - A/B Testing Pitfalls
• 01:16:00 - Navigating Acquisitions

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The Build with Mike O'Sullivan is a podcast produced by The Current which is owned and operated by The Trade Desk, Inc. Learn more: https://www.thecurrent.com/

Sincera was acquired by The Trade Desk, Inc.

Ad tech moves fast, but the real stories happen behind the scenes. This is where the architects of the industry come to talk shop.

Hosted by Mike O’Sullivan and co-host Ian Meyers - who first teamed up as the founders of Sincera - this is a builder-to-builder podcast for the founders, engineers, and innovators scaling the next generation of ad tech infrastructure. Drawing on their shared history of building in the trenches, Mike and Ian move past the headlines to explore technical hurdles, strategic pivots, and the candid realities of a complex ecosystem.

What you can expect from this series:

• Lessons from Mike and Ian’s founder journey with Sincera and beyond
• Technical Deep Dives: How the industry’s most influential tools are actually architected
• Unfiltered conversations on the challenges shaping the future of the stack

New episodes on Tuesdays. Follow The Build with Mike O’Sullivan on Spotify, Overcast, or wherever you get your podcasts.

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The Build with Mike O'Sullivan is a podcast produced by The Current which is owned and operated by The Trade Desk, Inc. Learn more: https://www.thecurrent.com/

Sincera was acquired by The Trade Desk, Inc.

Mike O’Sullivan (Co-Founder of Sincera and GM of Product at The Trade Desk) sits down with Michael Rubenstein, Co-Founder and Co-CEO of Firsthand, for a candid founder-to-founder conversation about innovation, risk, and leadership in the age of AI.

From DoubleClick to AppNexus (00:38) to Firsthand, Michael shares lessons from decades at the forefront of ad tech: what it means to build with purpose (04:50), how to hire and scale teams that thrive (14:15), and why the next wave of growth will come from brands who embrace AI directly (17:50).

This live episode was recorded at Advertising Week New York in October 2025.

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The Build with Mike O'Sullivan is a podcast produced by The Current which is owned and operated by The Trade Desk, Inc. Learn more: https://www.thecurrent.com/

Sincera was acquired by The Trade Desk, Inc.