Legacy System Modernization
Your systems work. They just need to work better. For more than 20 years, Coalesce has helped companies with application modernization that doesn't mean starting over: reducing risk while shipping real improvements.
Since 2006
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$320M+ lifetime client revenue powered by our software
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4+ year avg. client relationship
We specialize in brownfield development, improving the software you already have: making existing systems faster, easier to maintain, and ready for what's next.
Legacy application modernization, without the rewrite
Every agency wants to pitch you a greenfield rewrite. It's more billable hours, and they don't have to learn your codebase. But rewrites are risky, expensive, and often fail. There's a better way.
Your system has years of business logic baked in.
That "messy" codebase represents thousands of decisions about how your business actually works. A rewrite doesn't just replace code. It forces you to re-learn lessons you've already paid for. We'd rather build on what you know.
You can't pause the business while you rebuild.
Your team needs to keep shipping features. Customers need the system to stay up. A two-year rewrite means two years of maintaining parallel systems and delayed roadmaps. Incremental modernization lets you improve while you operate.
Your developers are tired of fighting the codebase.
Slow builds. Flaky tests. Fear of touching certain modules. Technical debt compounds until every change feels risky. We help you pay it down strategically, so your team can move fast again.
Services
A focused audit of your codebase, infrastructure, and pain points. We identify what's working, what's blocking you, and where to start.
Systematic improvements to code quality, architecture, and maintainability without stopping feature development.
Schema optimization, query performance, and migration to modern data infrastructure when needed.
Wrapping legacy systems with modern APIs so new applications can integrate without touching old code.
Moving from on-premise or outdated hosting to scalable cloud infrastructure, without downtime.
Addressing vulnerabilities, updating dependencies, and meeting current compliance requirements.
Process
We start by understanding your business: goals, constraints, existing systems (if any), and what success looks like. No 200-page audits.
A prioritized roadmap based on your constraints. What's urgent vs. important. What we can ship in weeks vs. what needs architectural work. Clear trade-offs, not hand-wavy estimates.
AI-augmented development with human review at every decision point. Whether we're starting fresh or working in your existing stack, you get senior engineers. No handoffs.
QA, deployment, and monitoring. We don't ship and disappear.
Ongoing partnership, not a handoff. We stick around to make it better.
Recent Case Studies
ERP for Manufacturing
A custom system that replaced Paperchef’s 40-year-old software stack and moved an entire warehouse operation in record time.
For Paperchef / Built with Ruby on Rails, Android, and AWS
24M+ Inventory Items Tracked
Tech for a Fabric Business
A smart, simple system that brought Zarin Fabrics, an 85-year-old warehouse, into the digital age.
For Zarin Fabrics / Built with Shopify and Stitch Labs
200,000+ Yards Stocked
Made by people who care how it turns out.
Behind every brand, product, and line of code we ship is a team you know by name. We use AI where it makes us faster. The judgment, the taste, and the final call stay with people.
Talk to our team
Talk to our team
Coalesce brought a rigorous development approach, meticulous attention to detail, and creative suggestions to the process. The team was clearly invested in the project's success and has become a trusted, valuable collaborator.
Morgan Brown
Inman News
FAQ
What industries do you work with?
We've modernized legacy systems in Financial Services, Healthcare, Education, Real Estate, Publishing, and Enterprise SaaS. The patterns are similar across industries: aging codebases, technical debt, and the need to move faster.
How long does a typical modernization project take?
It depends on scope and complexity. A technical assessment takes 2-4 weeks. Focused modernization sprints run 2-3 months. Larger transformations are ongoing partnerships, often 6-18 months. We'll give you a realistic timeline after discovery.
Is brownfield development the same as legacy modernization?
Close cousins. Brownfield development means building within an existing codebase and its constraints rather than starting fresh. Legacy modernization is brownfield work with a specific goal: making an aging system faster, safer, and easier to change. Either way, we work with what you have.
Do you replace our existing system or improve it?
We improve it. Our approach is incremental modernization, not rip-and-replace. We identify the highest-impact areas and address them systematically while your system stays running. Full rewrites are rarely the right answer.
When does a rewrite make more sense than modernizing?
Sometimes, but not often. A rewrite is worth considering when the platform can no longer be supported or secured, when the architecture can't carry something the business now depends on, or when nobody can safely change the code at all. If the system still runs the business and can be improved in pieces, we modernize it in place and replace only the parts that need it.
What technologies do you work with?
We're language-agnostic. We've modernized systems built in PHP, Python, Ruby, Java, and Node.js. The approach matters more than the stack. We'll work in whatever your system is built on.
Where is your team located?
We're headquartered in New York City, with partners in Nashville and South Florida. Working as one small senior team means faster turnaround without sacrificing quality or communication.
How do you price projects?
Most engagements start with a focused discovery phase, then move into monthly retainers for ongoing development and support. We scope work as fixed-fee or monthly retainers depending on the nature of the project. Full builds vary based on complexity. Many modernizations start with a technical debt assessment, which is fixed-scope and priced up front.
Ready to modernize without the risk?
We've powered $320M+ in lifetime client revenue with a lean team of senior engineers. Let's talk about what's slowing you down.