Migration Strategy and Planning: From Delphi to Next.js (Part 5 of 5)¶

The Complete Picture¶

We've covered TypeScript fundamentals, React components, and Next.js architecture. Now let's talk about what really matters: how to actually migrate your Delphi applications to the web without destroying your business in the process.

This isn't about code anymore. This is about strategy, risk management, and making smart business decisions.

The Delphi Developer's Dilemma¶

You're in a tough spot. You have:

Assets:

Applications that work perfectly
Years or decades of business logic
A team that's productive in Delphi
Clients who are (mostly) happy
Revenue that depends on these systems

Pressures:

Clients asking for web/mobile access
Difficulty hiring Delphi developers
Rising licensing costs
Modern UX expectations
Competition using newer platforms

Concerns:

"Can we afford a complete rewrite?"
"What if the migration fails?"
"Will our team adapt?"
"Can we maintain both systems during transition?"
"What if we lose clients during the change?"

These are legitimate concerns. Let's address them systematically.

The Myth of the Big Rewrite¶

Let's be clear: you probably shouldn't rewrite everything from scratch.

The big bang rewrite is tempting. Clean slate, modern architecture, fix all the old sins. But history shows that big rewrites often fail:

They take longer than estimated (always)
Requirements change during development
Business can't wait for years
Risk is concentrated in one massive project
You're maintaining two codebases (old and new)

There's a better way: incremental migration.

Strategy 1: The API Wrapper Approach¶

Concept: Keep your Delphi application, but expose its functionality through web APIs. Build new web interfaces that call these APIs.

How it works:

Your Delphi app continues running and working
You add API endpoints to Delphi (TMS XData, DataSnap, RAD Server, or custom)
Build Next.js frontend that calls these APIs
Users access web interface, but business logic stays in Delphi

Obviously, I am a bit biased here which tool to pick for the API layer as I just think TMS XData is the best fit for Delphi developers, but other options exist as well.

Advantages:

Minimal risk to existing system
Leverage years of proven business logic
Web access without full rewrite
Can migrate UI piece by piece

Disadvantages:

Two systems to maintain as Delphi executable stays
May hit performance limits
Keeps licensing costs

Best for: Getting web access quickly while planning longer-term migration.

Strategy 2: Parallel Development¶

Concept: Build new web version alongside Delphi version. Share database, but separate applications.

How it works:

Both apps access same database
Delphi app continues for power users
Web app for mobile/remote access
Gradually shift features to web version
Eventually phase out Delphi (or keep for specific users)

Advantages:

No disruption to current users
Learn Next.js with real projects
Can take time to get it right
Fallback if web version has issues

Disadvantages:

Duplicate effort for shared features
Database schema conflicts possible
Business logic duplication
Extended transition period

Best for: Large applications where users need different interfaces (power users vs mobile users).

Strategy 3: Module-by-Module Migration¶

Concept: Identify discrete modules in your application and migrate them one at a time.

How it works:

Analyze application into logical modules
Pick lowest-risk, highest-value module first
Migrate that module to Next.js completely
Users access that feature via web
Repeat with next module
Gradually replace entire system

Example module order:

Reporting (read-only, high value)
Data entry forms (medium complexity)
Dashboard/analytics
Complex workflows
Administrative functions

Advantages:

Continuous delivery of value
Learn and improve with each module
Risk is distributed
Can pause if needed
Users adapt gradually

Disadvantages:

Integration complexity between old and new
Some modules depend on others
Requires careful planning
Extended timeline

Best for: Complex applications with separable modules.

Strategy 4: New Features Only¶

Concept: Keep existing Delphi app as-is. All new features go into Next.js web app.

How it works:

Delphi app stays in maintenance mode
New development happens in Next.js
Share database or integrate via APIs
Users use both apps as needed
Delphi app slowly becomes legacy

Advantages:

Minimal disruption
Team learns gradually
Immediate benefit from web features
No forced migration of working code
Low risk

Disadvantages:

Users must use two systems
Integration overhead
Delphi app not going away
May not solve core problems

Best for: When existing app works well but needs expansion.

Assessing Your Application¶

Before choosing a strategy, understand what you have:

Questions to Ask:¶

Architecture:

How modular is your code?
How much is UI vs business logic?
Is database access centralized?
How many dependencies on VCL?

Business Logic:

How complex are your algorithms?
How much is calculation vs data movement?
Are validations embedded in UI?
Could logic be extracted to pure functions?

Data:

What database are you using?
How normalized is your schema?
Are there stored procedures?
How much business logic is in the database?

Team:

How many developers?
What's their experience level?
Willingness to learn new tools?
Available training time?

Clients:

How tolerant are they of change?
What features do they actually use?
Which features need web access most?
Can you run both systems during transition?

Creating a Realistic Timeline¶

Here's what migration typically takes (for a medium-complexity application). From experience, the numbers vary widely based on application size, complexity, and team experience. Use them to set expectations, not as guarantees. Also, look at the proportions rather than absolute numbers.

Assessment Phase: 2-4 weeks

Code analysis
Architecture documentation
Strategy selection
Team evaluation

Foundation Phase: 4-8 weeks

Next.js project setup
Database migration/optimization
Core components library
Development patterns established
Team training

First Module/Feature: 6-12 weeks

Implementation
Testing
User acceptance
Deployment
Monitoring

Subsequent Modules: 4-8 weeks each

Faster as team learns
Patterns are established
Components are reusable

For a 10-module application:

Assessment: 1 month
Foundation: 2 months
Modules: 5-7 months (doing 1-2 at a time)
Total: 8-10 months for complete migration

These are realistic timelines with professional guidance. Without guidance, add 50-100% (and even this range is conservative!) more time.

The Cost Reality¶

Let's talk money honestly:

DIY Migration Costs:

Developer time (biggest cost)
Training and learning curve
Mistakes and rework
Extended timeline
Opportunity cost of other features

Professional Migration Assistance:

Upfront consulting fees
But faster completion
Established patterns
Team training included
Reduced risk
Often costs less total than DIY when you factor in time

Example:

DIY: 2 developers × 15 months × $8k/month = $240k
Guided: 2 developers × 9 months × $8k/month + $40k consulting = $184k

The numbers are based on typical developer rates and timelines. Your mileage will vary, but the principle holds: The guided approach often costs less AND delivers faster.

Risk Management¶

Every migration has risks. Here's how to manage them:

Technical Risks:

Start with low-risk modules
Maintain old system during transition
Thorough testing before switchover
Have rollback plans
Monitor performance closely

Business Risks:

Get client buy-in early
Show progress frequently
Deliver value incrementally
Don't break existing workflows
Provide training and support

Team Risks:

Invest in proper training
Pair experienced with learning devs
Document patterns and decisions
Celebrate small wins
Accept learning curve exists

When to Bring in Professional Help¶

You might need professional migration consulting if:

You're not sure where to start
Timeline is critical (client deadline, competitive pressure)
Team has no web development experience
Application is complex or mission-critical
You've tried and gotten stuck
You want patterns established quickly

What professional help provides:

Assessment and Strategy¶

Analyze your Delphi codebase
Recommend specific migration approach
Create realistic project plan
Identify risks and mitigation

Architecture and Foundation¶

Design Next.js application structure
Set up database migration
Create component library
Establish coding patterns
Configure deployment pipeline

Team Training¶

TypeScript fundamentals
React patterns
Next.js best practices
Hands-on pair programming
Code review and guidance

Execution Support¶

Migrate first modules together
Guide complex business logic translation
Performance optimization
Security review
Production deployment

Handoff and Independence¶

Document architecture decisions
Create migration playbook
Train team to continue independently
Provide ongoing support channel

Typical engagement: 3-4 months intensive work, then ongoing support as needed.

My Migration Consulting Services¶

I specialize in helping Delphi development teams migrate to modern web platforms. This isn't generic web consulting—this is specifically for Delphi shops making this transition. I offer:

Initial Assessment¶

Comprehensive codebase analysis
Migration strategy recommendation
Realistic timeline and cost estimate
Risk assessment
No obligation to continue

Full Migration Partnership¶

Complete architecture design
Team training program
Hands-on development guidance
First module migration together
Ongoing support during full migration
Goal: Your team continues independently after foundation is set

Hourly Consulting¶

For specific questions or reviews
Code reviews and architecture advice
Troubleshooting and debugging
Team mentoring sessions

Why Work With Me¶

30 years Delphi experience (I understand your codebase)
Successfully migrated multiple Delphi applications
I speak both Delphi and Next.js fluently
With regards to language, I speak English and German having lived in both countries for many years
Focus on practical, business-driven solutions
Goal is your team's independence, not dependency

The Bottom Line¶

Migrating from Delphi to Next.js is achievable, but it's not trivial. It requires:

Strategic planning
Realistic expectations
Team commitment
Adequate time and resources
Professional guidance (for most teams)

The good news: Your Delphi expertise is valuable. The concepts translate. The learning curve is real but manageable.

The better news: The end result is worth it. Lower costs, wider reach, modern UX, easier hiring, and the ability to say "yes" when clients ask for web access.

Next Steps for You¶

Assess your situation:¶

Which applications need web access?
How complex are they?
What's your timeline?
What's your team's capacity?

Choose your strategy:¶

API wrapper for quick wins?
Parallel development for safety?
Module-by-module for thorough migration?
New features only for gradual transition?

Decide on guidance:¶

DIY with this series as foundation?
Professional assessment to start?
Full migration partnership?

Take action:¶

Don't wait for perfect conditions
Start small and learn
Build momentum with early wins
Iterate and improve

Ready to Start?¶

If you've read all five parts of this series, you understand:

Why TypeScript isn't foreign to Delphi developers
How React components work conceptually
How Next.js applications are structured
What migration strategies are available

Now it's time to apply this to your specific applications.

I'd love to talk with you about your situation. Even if you're just exploring options, a conversation can help clarify what's involved and what makes sense for your business.

Contact me for:

Free 30-minute initial consultation
Application assessment discussion
Migration strategy discussion
Team training information

Contact Information¶

Email: holger(at)flixengineering.com
LinkedIn: Holger Flick

Final Thoughts¶

The Delphi community has always been pragmatic. We solve problems. We build applications that work. We've adapted to changes before—from DOS to Windows, from BDE to FireDAC, from 16-bit to 64-bit.

This transition to web platforms is another adaptation. Not because Delphi is bad (it's still excellent), but because the market has moved. Our clients need web access. Our applications need to reach more users. Our businesses need to stay competitive.

TypeScript and Next.js aren't replacing Delphi—they're extending what we can build. And because Anders Hejlsberg designed both Delphi and TypeScript, the transition is more natural than you might think.

You can do this. Your Delphi expertise is an advantage, not a liability. The concepts you know translate directly. You just need to learn the syntax and patterns of a new platform.

You don't have to do it alone. Many Delphi shops have made this transition successfully. Learn from their experience. Get guidance where it makes sense. Build on proven patterns.

The future is web, but the wisdom is Delphi. Strong typing, component architecture, database expertise—these fundamentals don't change. You're not starting over. You're translating what you know into a new dialect.

Welcome to the next phase of your development career. Let's build something great together.

Thank you for reading this series. If it helped you understand the path forward, please share it with other Delphi developers facing similar decisions. Let's help each other navigate this transition successfully. Contact me!