## Abstract

Your client's legacy system works... mostly. It's held together with duct tape and prayer, but it's making money. They need new features. You want to use modern tools. They don't want to pay $150K for a complete rewrite. Sound familiar?

This talk covers the hybrid approach I've used across manufacturing, healthcare, and e-commerce clients: build new features in a new Laravel application while the old system keeps running. Share the database, maintain data consistency, deliver value immediately, and migrate features incrementally—only when there's budget and business justification.

You'll learn how to architect a shared database strategy between old and new systems, the migration patterns that minimize risk, the authentication bridges that let users move seamlessly between applications, and most importantly—how to sell this approach to clients who are terrified of "big bang" rewrites that could sink their business.

This is the pattern that lets you say "yes" to new feature requests without fighting battles over technical debt, gets you working in modern Laravel instead of maintaining ancient codebases, and gives clients a path forward that doesn't require bet-the-company risk.

## Key Takeaways

- **The Strangler Fig Pattern**: How to gradually replace legacy systems without rewriting everything at once
- **Shared Database Architecture**: Maintaining data consistency across old and new applications without breaking either
- **Authentication Bridges**: Seamless user experience between legacy and modern systems
- **Migration Decision Framework**: Which features to build new vs. leave in the old system
- **Incremental Deployment**: Shipping new features fast while managing risk
- **The Client Conversation**: How to sell this approach and get budget for gradual modernization instead of all-or-nothing rewrites

## Outline

1. **The Legacy System Trap** (5 min)
- Why complete rewrites fail (or never start)
- The consultant's dilemma: modern tools vs. legacy reality
- Real-world costs: "That'll be $150K and 6 months" vs. "Let's ship this feature next month"

2. **The Hybrid Approach: Building Alongside, Not On Top** (8 min)
- Strangler fig pattern overview
- Why this works for risk-averse clients
- Case study: Manufacturing system that needed modern features but couldn't afford downtime

3. **Shared Database Architecture** (12 min)
- Database connection configuration in Laravel for legacy schemas
- Handling legacy table structures and naming conventions
- Eloquent models that work with "ugly" legacy schemas
- Managing migrations: new app migrations vs. legacy schema changes
- Live demo: Laravel model connecting to legacy database

4. **Data Consistency & Integrity** (8 min)
- Event-driven updates between systems
- Database triggers for critical updates
- Queue-based synchronization patterns
- Handling conflicts when both systems write to shared tables
- Live demo: Trigger that keeps both systems in sync

5. **Authentication & User Experience** (8 min)
- Session sharing between applications
- SSO patterns with legacy auth systems
- Seamless navigation between old and new features
- Route/proxy strategies for unified URLs
- Live demo: User seamlessly moving between legacy PHP and new Laravel app

6. **The Migration Decision Framework** (8 min)
- Which features to build new (green field opportunities)
- Which features to leave in legacy (not worth migrating yet)
- Red flags: when NOT to use this pattern
- ROI calculation: when does migration pay for itself?
- Real example: Feature-by-feature cost analysis

7. **Deployment & Risk Management** (6 min)
- Deploying two apps that share data safely
- Rollback strategies when things go wrong
- Monitoring both systems during the hybrid period
- Testing: ensuring changes don't break either system

8. **The Client Conversation** (3 min)
- How to pitch this vs. "big bang rewrite"
- Budget conversations: incremental investment vs. massive upfront cost
- Managing expectations during the transition period
- Success stories: "We shipped 5 new features while planning the full migration"

9. **Q&A** (Variable)

## Real-World Examples to Reference

- **Manufacturing**: Purchase order tracking system - built new features in Laravel/Filament while legacy system kept records of over $6B in orders, gradually migrated modules as budget allowed

## Target Audience

Consultants, agency developers, and in-house teams maintaining legacy systems who need to deliver new features without getting stuck maintaining old code forever. Intermediate to advanced PHP developers who understand Laravel but struggle with the business/political side of modernization projects.

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**Session Length**: 40-50 minutes

**Session Level**: Intermediate/Advanced

**Tags**: Laravel, Legacy Modernization, Database Architecture, Consulting, Migration Strategies, System Architecture, Technical Debt

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**The Hook**: This is the talk that teaches developers how to say "yes" to new features without fighting the technical debt battle, and helps clients get real value without betting the company on a rewrite.