Building what's next (Interview)

Summary of Building what's next (Interview)

by Changelog Media

2h 0m•October 22, 2026
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Overview of Building what’s next (Interview)

This Changelog interview features Zeno Rocha, founder and CEO of Resend, on how he’s building an email platform for both humans and agents. The conversation moves from classic developer experience to the new reality of agent experience: machine-readable docs, standards-based APIs, better error handling, and workflows that let AI tools actually discover, use, and automate around Resend. Zeno also shares how Resend’s infrastructure, pricing, and product roadmap have evolved as the company scales to millions of users and increasingly serves a broader “builder” audience.

Key Themes

Email as a “boring” but powerful category

  • Zeno explains why he bet on email despite it seeming old, slow, and heavily protocol-driven.
  • His thesis: boring infrastructure businesses can still be highly successful if they deeply serve developers and usage scales over time.
  • Resend’s positioning is intentionally simple: “Email for developers.”
  • He says the company’s edge is empathy for builders and making a difficult domain feel easy.

The Stripe-like product philosophy

  • Resend is inspired by Stripe’s evolution from a hard problem into a clean API and developer substrate.
  • Zeno describes Resend’s approach as solving one problem well, then adding abstractions over time as customer needs mature.
  • He contrasts early no-code or dashboard-driven solutions with later API/SDK adoption as a startup grows.

Building for Agents: DX → AX

Agents need standards, not fancy UI

  • Zeno says many beloved DX features matter little to agents:
    • animated icons
    • keyboard shortcuts
    • polished visual flourishes
  • What agents do need:
    • discoverable docs
    • OpenAPI specs
    • machine-readable outputs
    • consistent error messages
    • standard headers and RFC compliance
    • rate-limit semantics that auto-retry cleanly

The “pricing slider” problem

  • A funny but important story: Claude and ChatGPT reportedly told users Resend was the most expensive email service.
  • The fix was to publish a markdown version of the pricing page via content negotiation.
  • Lesson: agents can’t interact with JavaScript-driven UI the way humans can, so websites need a non-visual, machine-friendly layer.

Practical AX improvements Zeno is making

  • Publishing OpenAPI JSON in /.well-known
  • Adding .md versions of content pages
  • Improving docs and FAQs for LLM consumption
  • Making logs and outputs available in JSON
  • Reworking rate limit behavior to follow RFC conventions
  • Testing how tools like Claude/OpenAI discover and evaluate Resend

Product and Infrastructure

Current stack and architecture

  • Resend runs primarily on AWS.
  • The team uses:
    • CDK for infrastructure
    • SQS for queues
    • SNS for email event handling
    • Datadog for observability and SLOs
    • Vercel for the dashboard and marketing site
  • Zeno says the company started with whatever let them ship fastest, then gradually replaced parts that no longer scaled.

The Go rewrite

  • Resend rewrote its high-concurrency “pipe” component in Go.
  • Why Go:
    • better concurrency for large broadcast sends
    • simpler binary deployment
    • easier reasoning about long-running services
  • The rewrite was gradual and transparent to users, but required multiple retries because of edge cases in headers, body formats, and international characters.

Handling email at scale

  • Resend supports:
    • transactional email
    • scheduled email
    • broadcasts
    • inbound/receiving email
    • automations
  • The hardest technical issue discussed was broadcast deliverability:
    • large sends must be broken into smaller batches
    • timing must be spread out to avoid Gmail throttling/spam placement
    • the system automatically shapes delivery based on volume and sender history

Inbound Email and Automations

Receiving email is harder than sending

  • Zeno says inbound email is a major pain point because:
    • MX records are tricky
    • users can break routing unintentionally
    • spam targeting wildcard addresses is constant
    • observability is weaker when inbound routing fails
  • He emphasizes that inbound was a top user request and that the team built it after repeatedly feeling the pain themselves.

Use cases for inbound

  • Trip management and parsing forwarded travel emails
  • BCC-based CRM ingestion
  • Agent inboxes
  • Support triage and draft replies
  • Wildcard inboxes for broad capture

Future plans

  • Resend is building a more full-featured inbound UI.
  • That UI will eventually have its own:
    • CLI
    • MCP server
    • agent-friendly workflows

Pricing, Free Tier, and Growth

Free tier as strategy, not charity

  • Resend offers a generous free tier:
    • 3,000 emails/month
    • 10,000 automation runs
    • daily caps and domain limits to control abuse
  • Zeno argues the free tier is essential for:
    • access and inclusion
    • developer adoption
    • long-term conversion
  • He says the company has invested heavily in anti-abuse systems because the free tier attracts bad actors too.

Paying customer scale

  • Resend passed 100,000 paying customers.
  • Zeno says total users are around 3 million.
  • He views that as a sign there’s still a much larger builder market to serve.

Pricing is part of the product

  • Zeno thinks about pricing constantly.
  • He sees pricing as a product surface, not just a business decision.
  • He admits some pricing choices, especially around marketing contacts, may need revisiting as usage patterns change.

OpenAI, Claude, and the New Go-To-Market Reality

Models now drive discovery

  • Zeno notes that recommendation engines inside Claude/OpenAI are increasingly driving signups.
  • Resend’s growth is now influenced by whether AI tools recommend it.
  • That creates a new requirement: products must be understandable not just to humans, but to models.

Multi-language, non-traditional builders

  • Resend’s users are no longer just “developers” in the classic sense.
  • He cites:
    • designers
    • marketers
    • founders
    • no-code builders
    • “builders” using tools like Bolt, Lovable, Cursor, etc.
  • The audience now includes people who can assemble products without being traditional programmers.

Team, Hiring, and Culture

Hiring priorities

  • Resend is hiring remote, globally distributed talent.
  • Zeno says they’re looking for:
    • email/deliverability experts
    • product engineers
    • people who care deeply about craft
  • The company is intentionally small and engineering-heavy.

Remote by design

  • The team is fully remote.
  • They have people across different regions, including APAC and Africa.
  • Resend emphasizes operational simplicity and distribution to support global customers.

Zeno’s Operating Style

He “dogfoods” everything

  • Zeno repeatedly stresses that he uses Resend constantly:
    • internal all-hands emails
    • investor updates
    • side projects
    • experimental workflows
  • He says he needs to feel the pain personally to build the right product.

Closed-loop automation

  • One of the most interesting stories:
    • he built a loop that reads downvotes on Resend’s in-app agent via PostHog
    • reviews the session context
    • generates draft PRs to improve tool calls and evals
  • He sees this as the start of “factory engineering” or closed-loop product improvement.

Notable Takeaways

  • Agents change the product surface. UI polish alone doesn’t matter if the model can’t use the product.
  • Standards win. RFC-compliant headers, JSON specs, and machine-readable docs matter more than proprietary conventions.
  • Email is still huge. Even “boring” infrastructure can have massive room to grow.
  • The builder market is expanding. The definition of “developer” is much broader than it used to be.
  • Pricing, docs, and error messages are now part of agent UX.
  • Resend is evolving from an email API into a broader comms platform, while still staying focused on email as its core.

Bottom Line

This interview is a deep look at how Resend is adapting to the agentic era without losing focus on its core mission. Zeno Rocha’s big idea is simple but powerful: if AI agents are going to use your product, you must design for their constraints the same way you designed for developers before them. That means better standards, better machine-readable surfaces, smarter defaults, and a product philosophy that treats infrastructure, docs, pricing, and automation as part of the same experience.