Overview
I led the design and launch of PayByPhone's first third-party advertising product. PayByPhone, a leading mobile payment solution used globally for finding and paying for parking, presented the core challenge of introducing monetization without disrupting the app’s fast-utility user flow. My data-driven approach, validated through extensive research and A/B testing, successfully delivered a 49% revenue lift on the final placement and achieved a projected $1.5 Million annual run rate in under six months of launch.
🎯 The Challenge: Capturing High-Value Engagement
PayByPhone wanted to unlock new revenue from a highly engaged moment: after users complete a parking transaction. The goal was to introduce relevant offers from partners to create a new revenue stream. The core challenge was complex: to integrate a highly effective third-party monetization feature while ensuring it was non-disruptive and maintained user trust in the app’s primary function (parking).
How might we design a seamless, optional way to present offers without disrupting the parking experience?
🛠️ Phase 1: Design Exploration and Concept Creation
I began by defining the opportunity within the existing parking flow, identifying the post-purchase moment as the ideal, high-intent placement. This timing was chosen because the user has completed the primary objective (paying for parking) and is likely open to additional services or offers. Also, placing offers after the payment confirms the transaction is complete doesn’t interrupt the core experience.
Existing PayByPhone Parking Flow
Placement Concepts (Overlay vs. Embedded)
I explored multiple initial design concepts, selecting candidates for validation that rigorously tested the two conflicting goals: maximizing revenue and minimizing friction.
Overlay Offer: Created to maximize visibility (the business goal), as the user would be required to interact with it (either accepting or closing the offer) to proceed.
Embedded Offer: Designed for lowest friction (the user goal), sitting passively under the active parking session card, making interaction optional.
My explorations for the multi-offer flow were also constrained by a technical limitation in the Rokt platform, specifically that users cannot return to a previous offer once seen. To manage user expectations and prevent confusion, I avoided standard carousel designs that involved swiping. Instead, I explored progress indicators. I ultimately chose the three-circle tracker over the '1/3' numerical format because the circles provided clearer visual feedback on progress and the inability to go back. The circles indicated progress by becoming solid when viewed, and remaining an outline otherwise.
📈 Phase 2: Qualitative and Quantitative Validation
This phase used both qualitative user interviews and quantitative usability testing to definitively choose the core placement design.
Step A: Qualitative Validation (User Interviews)
To validate the initial design concepts and understand user preference, I conducted moderated interviews with 15 participants. This research aimed to determine user perception of the offers and their preferred placement.
Methodology: Moderated user interviews were conducted with 15 participants to validate the designs.
Key Finding: Users strongly preferred Embedded because they felt greater reassurance their parking task was finalized before the offers appeared. The Overlay was perceived as a mandatory barrier, violating the Non-Intrusive Utility principle.
Step B: Quantitative Benchmark (Usability Testing)
I ran quantitative testing with a large number of users to get statistical significance on performance. The Overlay was included as a control group in unmoderated usability testing with 120 participants to provide a statistically significant measure of its impact.
Goal of Control Group: To provide quantitative evidence confirming that the Overlay introduced measurable friction compared to the Embedded designs.
Key Findings: Task times quantitatively confirmed the Overlay added measurable overhead. Crucially, all tested designs achieved Excellent usability (SUS scores above 90).
👉 Decision: The Embedded placement was definitively confirmed as the foundation for the final product.
Overlay Vs Embedded Offer Designs
🚀 Phase 3: Launch and Live Optimization (A/B Testing)
With the Embedded placement definitively validated, we moved directly to execution. I decided to conduct live A/B testing with 2 variations to gather conversion-specific data. This was essential because unlike usability testing, which measures friction, live testing measures actual user behavior specifically, whether users would click on the offer and which design variant led to the highest financial conversion. We executed two key live experiments:
A/B Test 1: CTA Placement (Stacked vs. Side-by-Side)
I explored the Side-by-Side layout specifically to reduce vertical screen space usage. This was tested against the standard Stacked layout to determine which format provided superior tapping ease and visual prominence for conversion.
Result: Stacked CTA won, delivering a 49% higher revenue impact.
A/B Test: CTA Placement (Stacked vs. Side-by-Side)
A/B Test 2: Progress Tracker (With vs. Without)
I tested if revealing the full offer count on the very first screen would improve overall engagement or create friction. The test aimed to see if immediate transparency increased engagement and conversion.
Result: The option with the Progress Tracker won, delivering a 1.9% revenue lift.
A/B Test: Progress Tracker (With vs. Without)
🔄 Final Polish: Post-Launch Design System Update
Following the successful deployment and A/B testing phase, PayByPhone launched a new version of its design system. I took the responsibility of ensuring the post-purchase offers were fully compliant with the new visual standards.
Final Design with Design System Update
🏆 Results & Impact
The final design using the Embedded placement, Stacked CTA, and Progress Tracker delivered rapid, verifiable success across business and user metrics.
Financial Impact: The feature achieved a projected $1.5 Million annual run rate in less than six months from launch.
Growth: The Positive Engagement Rate successfully reached the Rokt benchmark in North American markets.
Adoption: The team celebrated reaching first 100,000 monthly users utilizing the offers.
This project validated that high-impact monetization can be successfully layered into a core utility flow through strategic, data-driven design.
Post-Launch Success: Team Celebration After Achieving Initial Milestones