Navigating Billing System Complexities

How much can legacy code tell us beyond just functionality? Julia López, Senior Software Engineer at Harvest, believes that even small details—such as white spaces, variable names, and formatting choices—can reveal a system’s history.

In this episode, Julia and Robby discuss the importance of refactoring and how a strong engineering culture can make or break a team's ability to maintain and improve software over time. Julia shares her experience leading a multi-year overhaul of Harvest’s billing system, balancing stakeholder expectations while ensuring the rewrite delivered real value.

They explore how refactoring decisions evolve as teams grow, how to mentor newer developers to feel empowered to make changes, and why Julia doesn’t always trust her own estimations (for good reason). She also opens up about the complexities of transitioning a live billing system while supporting customers, finance teams, and engineering operations—all without disrupting payments.

Beyond technical decisions, they also dive into the challenges of communication in remote teams, the value of autonomy in software development, and how teams can make a case for technical debt reduction even when leadership isn’t prioritizing it. If you've ever struggled with refactoring legacy systems or advocating for improvements, this conversation is packed with practical lessons.

💡 Key Topics & Timestamps

• [00:00:22] Meet Julia López – Her background, role at Harvest, and passion for refactoring.
• [00:00:42] What Makes Software Maintainable? – A test suite you can trust and an engineering culture that values refactoring.
• [00:06:31] Leading Harvest’s Billing System Overhaul – Why a full rewrite made more sense than incremental improvements.
• [00:09:54] The Hidden Complexity of Billing Systems – Managing ACH, credit card, and invoice payments.
• [00:14:05] The Fear Factor in Large-Scale Refactoring – Why organizations hesitate and how to push forward.
• [00:18:47] Communication Challenges in Remote Teams – Why documentation and transparency matter beyond GitHub.
• [00:28:30] Finding and Enforcing Engineering Patterns – How teams can encourage consistency in a constantly evolving codebase.
• [00:35:45] Why Autonomy Matters for Developers – Learning through struggle and when to ask for help.
• [00:45:25] Advocating for Refactoring When Leadership Says No – Julia's approach: "Ask for forgiveness, not permission—but estimate higher."

🔗 Resources Mentioned

• Harvest – Julia's company
• Radical Candor by Kim Scott
• The Making of a Manager by Julie Zhuo
• Stripe – The payment processor used in Harvest’s billing system
• Git Blame – A tool for understanding code history

📢 Connect with Julia López

• Julia's Website
• LinkedIn
• GitHub
• BlueSky

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