You really, really, really don't need an effect! I swear!
Before you write another useEffect, ask one question: is this syncing with an external system? If not, there's a better way.
Lead Engineer @ Rover.com International Speaker Podcast Host Workshop Facilitator
Neciu
Dan
14 years building exceptional frontend experiences. Now traveling the world to share what really matters about
security, scale, testing, and the future of engineering.
33+ Conference Talks
15+ Countries
50+ Podcast Episodes
500+ Workshop Students
Who I Am
I'm a seasoned software engineer with over 14 years in the tech industry — currently Lead Engineer at Rover.com. Previously Staff Engineer and Technical Co-Founder at CareerOS. I care deeply about testing, accessibility, security, and building software that lasts.
Beyond the code, I'm an international speaker who has taken the stage at React Rally, React Summit, WeAreDevelopers World Congress, Frontmania, KCDC, Techorama, and many more. My talks aren't slides — they're stories. Honest ones, with scars.
I'm the host of Señors at Scale, a podcast for senior engineers navigating the messy reality of scaling applications and teams. And I created the Lizard to Wizard engineering excellence workshop — a sold-out intensive that bridges the gap between "I can code" and "I can engineer."
Based in Barcelona 🇪🇸
On Stage Around the World
🎙️ The Podcast
Señors
at Scale
Real conversations with senior engineers about what it actually takes to scale applications, teams, and careers. No hype. No fluff. Just hard-earned lessons from engineers who've been in the trenches.
- 🎯50+ in-depth episodes with engineering leaders
- 🔧Topics: scaling, architecture, testing, leadership & AI
- 🌍Guests from Spotify, Vercel, Google, Netflix & more
- 📊1,000+ monthly listeners across 40+ countries
Sold Out
3× in a row
3× in a row
🧙♂️ The Workshop
From Lizard
to Wizard
The sold-out engineering excellence intensive that bridges the gap between "I can code" and "I can engineer." A full-day hands-on workshop for engineers who want to stop being surprised by senior interviews — and start owning them.
- Algorithmic Thinking Practical problem-solving techniques, not LeetCode grinding
- System Design at Scale How to think about distributed systems and trade-offs
- Security Fundamentals OWASP Top 10, XSS, CSRF, and real-world attack patterns
- Accessibility Excellence WCAG, ARIA, and building genuinely inclusive interfaces
- Observability & Design Patterns Monitoring, logging, and the patterns that survive production
Global Speaking Circuit
Talk Directory
From React Rally to WeAreDevelopers World Congress — every talk, every stage, every topic.
33 Talks
15+ Countries
2 Upcoming
2026
Architecture ● Upcoming
Micro Frontends & Me, a Love Story
From skepticism to scale: the real trade-offs of adopting micro-frontends, the good, the bad, and the tooling that makes it work.
Architecture ● Upcoming
Lizard to Wizard
The engineering excellence workshop in talk form — bridging the gap between 'I can code' and 'I can engineer' with practical, battle-tested techniques.
React
How Not to Use TanStack Query
The anti-patterns, misuses, and common mistakes engineers make with TanStack Query — and how to fix them for real.
Architecture
Micro Frontends & Me, a Love Story
An honest story of going from micro-frontend skeptic to practitioner — the architecture choices, the failures, and eventual success.
React
How Not to Use TanStack Query
The most common TanStack Query mistakes and misuses — illustrated with real examples and practical fixes.
Architecture
Micro Frontends & Me, a Love Story
From skepticism to scale: what micro-frontends actually look like in production, and why they're worth it.
Architecture
Micro Frontends & Me, a Love Story
From skepticism to scale: the real trade-offs of adopting micro-frontends and the tooling that makes it work.
2025
AI & Future
Surviving the AI Apocalypse
Harnessing AI to become a more productive, future-proof developer — practical strategies for staying relevant as AI transforms software development.
React
Scaling a JavaScript App from 0 to a Billion Users
The full playbook: choosing the right tech stack, building a design system, and optimizing React performance at massive scale.
React
Scaling a JavaScript App from 0 to a Billion Users
Tech stack selection, architecture, design systems, automated releases, and React performance — all the decisions that matter at scale.
React
Scaling a JavaScript App from 0 to a Billion Users
How to scale a JavaScript application while keeping the codebase clean, the team aligned, and the product fast.
Frontend
Pixels, Promises & Panic: Production Nightmares
Browser bugs, deploy disasters, and the moments every frontend engineer wants to forget — but needs to hear.
AI & Future
The Future of Programming
How AI tools are reshaping the way we write code — and what that means for engineers building tomorrow's software.
2024
Frontend
Pixels, Promises & Panic: Production Nightmares
Real-life catastrophes from the frontend trenches — told with humor, empathy, and actionable takeaways.
React
Scaling a JavaScript App from 0 to a Billion Users
How to keep your codebase clean, your team aligned, and your application fast when everything is exploding.
Frontend
Pixels, Promises & Panic: Production Nightmares
From browser bugs to accidental data loss — frontend horror stories that will make you audit your deploy process.
AI & Future
Surviving the AI Apocalypse
Practical strategies for staying relevant and productive as AI transforms the software development landscape — presented at the world's largest dev conf.
Security
Security in Frontend Applications
Building secure JavaScript applications when frameworks alone aren't enough to protect your users.
Security
Security in Frontend Applications
The most common vulnerabilities in modern front-end apps and the practical steps to eliminate them.
Architecture
Micro Frontends & Me, a Love Story
The honest trade-offs, architecture choices, and lessons learned from adopting micro-frontends at scale.
React
Scaling a JavaScript App from 0 to a Billion Users
The full scaling playbook presented in front of Barcelona's developer community.
Security
Security in Frontend Applications
The most dangerous and overlooked security vulnerabilities in modern front-end applications.
2023
Architecture
Micro Frontends & Me, a Love Story
From skeptic to practitioner: an honest story of micro-frontend adoption, failure, and eventual success.
React
Scaling a JavaScript App from 0 to a Billion Users
Real-world architecture decisions for scaling while maintaining code quality and developer happiness.
Security
Security in Frontend Applications
Building secure JavaScript applications in a world where attackers are more creative than ever.
Testing
Modern Testing Practices in Frontend Applications
Testing practices beyond the Testing Pyramid — practical approaches for delivering clean, bug-free code.
Culture
Bridging the Interview Gap: Engineering the Perfect Fit
Both sides of the interview table: how to prepare authentically and how to spot genuine engineering talent.
Architecture
Micro Frontends & Me, a Love Story
An honest story of going from micro-frontend skeptic to practitioner — the good, the bad, and the tooling.
Culture
Culture Hack: Building Bridges in Dev Teams
Navigating cultural differences in multi-cultural, remote-first software teams — feedback, deadlines, and inclusivity.
JavaScript
So… What's New with JavaScript?
New Array methods, temporal date API, import attributes — all the modern JS features you should be using right now.
Testing
The Perfect Unit Test
Why unit tests matter, how to write the perfect one, and most importantly — when to write it.
2022
Accessibility
The Bare Minimum: Accessibility in Web
What accessibility features web developers must implement — and exactly how to do it without over-engineering.
Frontend
The Perfect Design System
How to build a design system in Figma and translate it faithfully into a scalable, maintainable frontend application.
Work Experience
Lead Engineer
- Leading frontend engineering at the world's largest network of pet sitters and dog walkers — 2M+ users
- Driving architectural decisions, performance standards, and security practices across the engineering org
- Mentoring engineers and establishing team-wide best practices for accessibility, testing, and code quality
Chief Staff Engineer & Technical Co-Founder
- Orchestrated full CI/CD infrastructure on GCP and Netlify — increased deployment velocity by 150%
- Built the product from zero to production in under 2 months, leading Sales, Product, and Engineering integration
- Initiated a Design System and component library — delivered 50+ reusable components across all products
- Integrated LLM models (Gemini, OpenAI) for AI features — boosted engagement 3× and raised 8-week retention from 18% to 38%
- Directed company-wide roadmaps as C-level co-founder — scaled MAU by 300% across 6 launched initiatives
Senior Software Engineer
- Improved Web Core Vitals from 50% green to 90% green across LCP, FID, and CLS
- Led Product Filtering initiative — boosted CVR by 3% and Organic Traffic by 20%
- Built the full Authentication Flow (Google/Apple sign-in) — accelerated sign-up rates by 75%
- Introduced Observability dashboards and monitors — reduced app errors by 30%
- Co-ordinated CI/CD pipeline with Performance Budgets — improved team velocity by 50%
Senior Product Engineer
- Led full migration of legacy AngularJS codebase to StencilJS and React — 90% of application migrated
- Implemented Design System and Component Library with 100+ components
- Improved filtering experience — increased CVR by 1.2%
- Responsible for CI/CD pipeline across 4 frontend applications; advocated for XP practices (TDD, mob & pair programming)
From the Blog
View all posts » 
10 React tips I wish someone had told me before I mass-produced bugs
After running a 30-day React deep-dive, these are the 10 patterns that changed how I write components, manage state, and think about performance.
Build your own shimmer skeleton that never goes out of sync
Skeleton screens break every time you touch the UI. Here's how to build one that reads the DOM and keeps itself in sync automatically.
Start naming your useEffect functions, you will thank me later
I started naming my useEffect functions about a year ago. It changed how I read components, how I debug them, and eventually how I structure them.
A tech breakdown of Server-Sent Events vs WebSockets
Benefits and drawbacks of Server-Sent Events vs WebSockets, and when its better to use ach protocol based on your situation.
How to steal npm publish tokens by opening GitHub issues
A chain of vulnerabilities and pretty clever attack strategies led to the compromise of the Cline CLI. Let me explain what happened and what you can do to protect yourself.