When the Hummingbirds team first reached out to Customer.io and Optiblack, they weren’t shopping for yet another tool or a few weeks of consulting. They were trying to escape a fragile growth engine held together by HubSpot hacks, manual workflows, and more operational risk than they were comfortable with.
They wanted something different: a growth stack they could actually own—a system where product behavior, communication, and analytics spoke the same language.
This is the story of how they got there.
For a long time, HubSpot sat at the centre of Hummingbirds’ world. It was the system of record for brand communication and email. Creators received welcome flows, Instagram connect prompts, and engagement nudges. But underneath, the machinery was clunky.
Critical emails were driven by CRM properties and brittle workflows instead of what really mattered: what creators did in the product.
Three problems kept surfacing:
Hummingbirds knew this wouldn’t scale past 40,000+ creators.
Customer.io emerged as a candidate to replace HubSpot for engagement. Mixpanel was chosen to own behavioral analytics. And Optiblack was brought in to design and implement the connective tissue between all of it.
The mandate was clear: build a stack that could power event‑driven growth at scale—without turning the team into permanent tool operators.
The journey began with exploration, not implementation.
Early Customer.io conversations focused on a flexible trial: how to test the platform safely with dummy data, small amounts of real data, or synthetic CSV uploads. Meanwhile, Hummingbirds’ tech lead, Nick, dug into integration requirements across their Zero Data Platform (ZDP), Mixpanel, and even Amplitude.
In the background, a bigger decision loomed: which CDP should sit at the center of the data layer?
Customer.io’s own CDP, Segment, and RudderStack were all on the table. After weighing cost, flexibility, and ownership, the team aligned on a simple hierarchy:
CDP → Analytics → Engagement
RudderStack (open‑source) → Mixpanel → Customer.io
This order of operations mattered. It meant:
The second decision was about speed.
Hummingbirds lacked the spare engineering capacity to architect and ship this foundation quickly. Optiblack proposed a focused, 5–6 week project that combined:
After a series of scoping and negotiation calls, the teams landed on a $6,500 implementation, partially offset by Customer.io partner credits. The SOW was clear and bounded:
For Hummingbirds, the business case was easy to justify: compress months of design and implementation into a few weeks, and ship a growth stack that would otherwise be perpetually “in progress” alongside product work.
The first real friction point came early—and it had nothing to do with tools.
Optiblack’s preferred working model was to get branch‑level access to Hummingbirds’ codebase so they could wire in event instrumentation directly. Hummingbirds, however, had assumed a cleaner separation: Optiblack would handle the external tools, and their own engineers would handle emission of events from the app.
This misalignment forced a tough choice:
Rather than lurch to one extreme, they settled on a hybrid.
Optiblack would:
Hummingbirds’ engineers would:
The result was a governance win: Hummingbirds retained control of their product code while fully leveraging Optiblack’s architecture expertise.
Because most creator behavior happens in the Next.js web app, the team had to face a tough reality: client‑side tracking is fraught.
Two issues stood out:
Optiblack recommended a more deliberate approach:
The team accepted that some client‑side data loss (10–30%) was inevitable, but they also understood the trade‑offs: this architecture significantly reduced risk while staying achievable within their Q4 timeline. More advanced server‑side cohort events could wait for a later phase.
For Hummingbirds, this phase transformed analytics from a black box into a set of conscious, documented trade‑offs.
Initially, Mixpanel’s native SDK seemed like the natural default for client‑side tracking.
But as the architecture sharpened, Optiblack surfaced a crucial detail: Mixpanel’s out‑of‑the‑box integration with Customer.io syncs cohorts, not raw events. If Hummingbirds wanted Customer.io to power truly event‑driven lifecycle automation, they would eventually face a nasty surprise—duplicating event implementation just to feed Customer.io.
Instead of walking into that trap, they changed course.
RudderStack became the primary event pipe:
This decision protected Hummingbirds from exactly the sort of long‑term technical debt many teams only notice once they’re deep into a second or third integration.
Over time, the architecture matured into a pragmatic, layered system:
This layering introduced some latency—up to ~24 hours for derived properties—but that was an acceptable trade‑off. Most of Hummingbirds’ communications were lifecycle‑oriented, not ultra‑time‑sensitive transactional alerts.
The payoff was meaningful: Customer.io could operate with rich, behavioral context without corrupting the integrity of the analytics layer.
With the data plumbing in place, the team could finally address one of the most visible wins: moving creator email flows from HubSpot to Customer.io.
They started with the most impactful pieces:
But the biggest risk wasn’t technical. It was reputational.
Hummingbirds had ~36.7k contacts to move and a domain reputation to protect. A clumsy migration could easily tank deliverability.
Together, the teams designed a phased domain warm‑up strategy:
This careful choreography preserved a healthy sending domain while unlocking Customer.io’s full capacity for 2026.
With events flowing and infrastructure humming, the next challenge was deceptively simple: make the data usable to humans.
Optiblack and Hummingbirds invested heavily in the upfront tracking plan and taxonomy:
Perfection was explicitly off the table. The goal was to get to “close enough” fast, with a framework that would age well as the product evolved.
From there, Optiblack shipped:
The result was a step‑change in autonomy: Jordan, Callie, and the broader growth team could answer their own questions without queuing up requests for engineers or consultants.
No real‑world implementation is perfect, and Hummingbirds’ was no exception.
Several integrity issues surfaced:
Rather than sweep these under the rug, the team tackled them openly:
By the end of this phase, the data was directionally trustworthy and explainable. Everyone understood the limitations, and those limitations were documented—not hidden.
By January, the narrative shifted from “build and fix” to “enable and own.”
Hummingbirds made a strategic call: this system would not live perpetually in a consultant’s notebook. It would be owned in‑house.
The plan for the final stretch was straightforward:
Optiblack’s final deliverables included:
By the end of the engagement, Hummingbirds had:
Behind the story, the numbers tell their own version:
On the technical side, the architecture now looks like this:
The tracked events capture the full creator lifecycle—from sign‑up and profile completion, through campaign discovery and participation, all the way to content uploads, payments, and email engagement.
Segmentation now includes:
With 95%+ profile integrity and retroactively corrected tags, Hummingbirds finally had a single, reliable user definition across tools.
Looking back, several lessons stand out:
Hummingbirds’ journey was never just about replacing HubSpot.
It was about transforming how growth itself was instrumented, measured, and automated—and making sure the company, not its vendors, owned that capability.
By January 2026, Hummingbirds had:
The payoff was substantial: reduced dependency on HubSpot, actionable growth insights at their fingertips, and a scalable growth stack ready for the next stage of the marketplace.
In story terms, Hummingbirds didn’t just install tools. They rewrote the operating system for how their marketplace grows.