Spa Space was the most ambitious and challenging engagement of my career - a three-sided wellness marketplace connecting consumers with service professionals at facilities across the US. What began as a contract developer role through Toptal evolved rapidly: within two months, my technical strategy proposal earned me a Principal Engineer title, and when that strategy attracted acquisition interest, I found myself performing CTO duties while coordinating development across multiple agency teams.

The technical architecture I defined was deliberately built for volatility. Knowing the business requirements would shift, I designed a distributed system of 45+ microservices using Dapr for service-to-service communication, with each service owning its own MongoDB database. This flexibility proved essential - the platform survived an acquisition, multiple strategic pivots, and three separate agency engagements without requiring architectural changes. When agencies introduced technical debt, the core team could rebuild their six months of work in a single month.

The integration challenges were substantial. For example, Stripe Connect handled payment collection and distribution across three beneficiaries per booking - the consumer, professional, and facility each had their own payout requirements. Service menus cascaded from organisations to facilities to individual professionals, with override logic at each level. HubSpot integration was event-driven, SendGrid and Twilio unified under a single notification service with channel-based routing.

One of the hardest lessons came from coordinating external agency management. I warned the executive board that third-party agencies would consume budget without delivering value - and across three sequential engagements (India, Dallas/Brazil, Boston/Colombia), that prediction proved accurate. Each agency was management-heavy and developer-light, requiring me to personally train and mentor their resources while lacking the authority to make binding decisions. The core team I assembled - myself, a trusted contractor colleague, and an exceptional in-house frontend engineer - consistently outperformed agencies that cost significantly more.

The project ultimately failed to launch due to budget exhaustion on agency fees, exactly as I had predicted. But the architecture succeeded: we achieved 90% code coverage through SonarCloud integration, eliminated the SQL injection vulnerabilities and anti-patterns of the inherited v2 system, and built a platform that flexed with every business pivot. When the third agency departed, they informed the company how much behind-the-scenes work I had done to upskill their developers - and the company formally granted me the Fractional CTO title I had been performing all along.

The lesson I carry forward: how you enter a company matters as much as what you achieve. Authority without title is exhausting; I spent years doing the right things without the power to prevent the wrong decisions. That experience shapes how I approach every engagement now.