Jose Calderon
Lead Software Engineer at JP Morgan Chase
In this episode of Señors @ Scale, host Neciu Dan sits down with Jose Calderon — Lead Software Engineer at JP Morgan Chase, conference speaker, and Java/Spring community leader — to dive deep into refactoring vs rewriting at scale, how to track and justify architecture decisions, and the testing strategies that keep enterprise systems reliable.
Main Takeaways from my conversation with Jose:
🛠 Refactor if you’re in control, rewrite if you’re not.
If your team understands the codebase, has tests, and changes are predictable, refactor. If one line breaks something unrelated or the code is untestable, it’s rewrite time — but keep the scope locked and avoid “bonus” features.
🚧 Stabilize before you touch it.
Before a rewrite, Jose’s teams add telemetry, fix recurring issues, and lock down changes so the new build isn’t chasing a moving target.
💾 Your code is only as good as your decision history.
He uses Architecture Decision Records (ADRs) — stored in source control — to document the why behind each decision, making it easier to evolve or roll back choices later.
📈 Tests are documentation too.
Unit tests should read like an executable spec, explaining what the code does before you even open the class.
🎯 Synthetic testing catches breakage early.
Injecting canary events into critical paths — even in production when allowed — validates integrations before customers feel the pain.
🔥 Chaos engineering builds resilience.
Game-day drills prepare teams to recover fast when production crashes inevitably happen.
👨🏫 Mentorship multiplies impact.
By teaching final-year students how to lead and coach, Jose helps prepare them for the messy realities of enterprise engineering.
🎤 Also in this episode:
- How to pick the right complementary stack with Java
- Turning conference talks into memorable stories (Gaudí, aloe vera, and more)
- Why AI won’t replace devs, but devs using AI will replace those who don’t
- How gaming helps avoid burnout
Episode Length: 1 hour and 6 minutes of pragmatic engineering lessons on managing large-scale code changes
💡 More Recent Takeaways
Señors @ Scale host Neciu Dan sits down with Daishi Kato, the author and maintainer of Zustand, Jotai, and Valtio — three of the most widely used state management libraries in modern React. Daishi has been building modern open source tools for nearly a decade, balancing simplicity with scalability. We dive deep into the philosophy behind each library, how they differ from Redux and MobX, the evolution of the atom concept, and Daishi's latest project: Waku, a framework built around React Server Components.
Señors @ Scale host Neciu Dan sits down with Vlad Khononov, software architect, keynote speaker, and author of Learning Domain-Driven Design and Balancing Coupling in Software Design. Vlad has spent over two decades helping teams untangle legacy systems, rebuild failing architectures, and bring clarity to messy business domains. This conversation cuts through the hype around DDD and microservices, focusing on the mechanics of bounded contexts, coupling, business alignment, and architectural evolution.
Seniors @ Scale host Neciu Dan is joined by Bramus Van Damme, Chrome Developer Relations Engineer at Google. As a leading voice in CSS and Web UI, Bramus dives into the future of the web, breaking down the mechanics, performance, and cross-browser status of transformative new features like View Transitions, Scroll-Driven Animations, Anchor Positioning, and Custom CSS Functions. He offers a rare look into the inner workings of Chrome DevRel, the standardization process through the CSS Working Group, and how the multi-browser 'Interop' effort is accelerating web development.
Señors @ Scale host Neciu Dan sits down with Liran Tal, Director of Developer Advocacy at Snyk and GitHub Star, to unpack NPM malware, maintainer compromise, MCP attacks, toxic flows, and why AI-generated code is statistically insecure without the right guardrails. Liran shares real incidents from the Node and open source ecosystem, how Snyk and tools like NPQ help developers build safer workflows, and why security at scale starts with developers, not firewalls.
📻 Never Miss New Takeaways
Get notified when new episodes drop. Join our community of senior developers learning from real scaling stories.
💬 Share These Takeaways
Want More Insights Like This?
Subscribe to Señors @ Scale and never miss conversations with senior engineers sharing their scaling stories.