Legacy System Integration in 2024: Top 4 Methods, Pros & Cons

Integrating legacy systems with modern technologies is a crucial challenge facing many enterprises today. Legacy systems refer to old, outdated technologies that companies still rely on for mission-critical business functions. According to Gartner, the average large enterprise has over 1,100 legacy applications. But over 50% of legacy modernization initiatives fail due to integration hurdles.

In this comprehensive guide, we will explore the top four integration techniques used to connect legacy systems with new applications and platforms. We‘ll evaluate the pros and cons of each method – Enterprise Service Bus, APIs, Integration Platforms, and Robotic Process Automation. We‘ll also provide real-world examples and best practices to help you successfully integrate legacy systems in 2024 and beyond.

Why Legacy System Integration Matters

Before we look at specific techniques, it‘s important to understand why integrating legacy systems is so challenging yet crucial for enterprises today:

  • 80% of IT budgets go towards maintaining legacy systems – Billions are spent each year just to keep legacy systems running. This hampers innovation investments.
  • Security vulnerabilities abound – Over 60% of breaches involve compromises via legacy systems. Their lack of modern security makes them an easy target.
  • Cloud migration roadblocks – 92% of organizations face problems moving legacy systems to cloud platforms. This slows cloud adoption.
  • Compliance struggles – Legacy systems increasingly fail to meet modern regulations around privacy, access control, and more. Fines and penalties result.
  • Skills shortages – Legacy platforms like COBOL and mainframes have severe talent shortage with expertise retiring faster than it can be replaced.

Integrating legacy with modern systems addresses these challenges while unlocking innovation and new capabilities leveraging latest technologies. Now let‘s examine popular integration techniques:

1. Enterprise Service Bus (ESB)

The enterprise service bus (ESB) architecture provides middleware to integrate disparate systems as centralized services. ESBs enable communication between legacy systems using adapters and message routing.

For instance, a major US insurance firm uses an ESB to connect policy and claims systems running on mainframes to web and mobile apps built on modern cloud platforms. This allows them to build innovative customer experiences while integrating with core legacy systems.

Key Pros

  • Centralized integration minimizes connections between systems
  • Decouples systems by abstracting interfaces behind adapters
  • Support for orchestrating complex transaction workflows
  • Built-in message routing, transformation, monitoring capabilities

Key Cons

  • Single point of failure risks from centralized architecture
  • Complexity in managing middleware infrastructure
  • Not ideal for external-facing integrations
  • Limited real-time integration capabilities

So ESBs work well when integrating multiple internal legacy systems. But modern distributed architectures like APIs and iPaaS have superseded ESBs for most external integrations.

2. APIs

Exposing backend legacy systems as APIs enables integrating them with modern applications and even external partners. APIs act as a facade to abstract complex legacy system logic behind modern RESTful interfaces.

For example, leading airlines use API gateways to expose availability and booking APIs from their legacy reservation systems. This enables fast integration with travel aggregators and mobile apps.

Key Pros

  • Enable real-time integration with internal and external systems
  • Abstract away legacy system complexity behind modern APIs
  • Facilitate innovation via API ecosystem across partners
  • Manage legacy API integration using modern API gateways

Key Cons

  • Upfront effort for API development and documentation
  • Added API management overhead for security, traffic, versions etc.
  • Tight coupling between systems if APIs not designed properly
  • Legacy API versioning challenges during change management

Overall, APIs provide the most flexible and future-proof approach to integrate legacy systems.

3. Integration Platform as a Service (iPaaS)

Integration platform as a service (iPaaS) offers pre-built connectors, templates and tools for integrating applications without coding. iPaaS provides cloud middleware to connect legacy systems to cloud platforms.

For example, a healthcare ISV used an iPaaS to rapidly integrate their legacy practice management system with new cloud clinical apps. This accelerated their migration to cloud while retaining support for legacy system dependencies.

Key Pros

  • Faster no-code integration approach
  • Pre-built connectors and adapters for common legacy platforms
  • Seamless integration between legacy systems and cloud apps
  • Reduced legacy integration costs and efforts

Key Cons

  • Potential vendor lock-in risks
  • Limited flexibility compared to custom coding
  • Integration performance overhead
  • Subscription costs involved

So iPaaS offers faster integration times but evaluate thoroughly across technical and business requirements.

4. Robotic Process Automation (RPA)

RPA tools can integrate legacy systems by automating repetitive tasks like data transfers. RPA bots log into legacy system UIs, scrape data, and move it to destination systems.

For instance, banks use RPA bots to extract data from legacy banking systems and populate forms in new customer onboarding systems, accelerating legacy modernization.

Key Pros

  • Quick integration with no disruption to legacy systems
  • Adapt even as legacy system UIs change
  • Help migrate legacy data to modern databases
  • Audit trails improve security and compliance

Key Cons

  • Only works for legacy systems with accessible UIs, APIs still needed
  • Bot failure risks for business processes
  • Ongoing bot maintenance is required
  • Scalability limitations at high transaction volumes

RPA provides a handy option for UI-based legacy data migration but has scalability and security limitations compared to API and iPaaS integrations.

Comparison of Legacy Integration Techniques

Here is a quick comparison of the pros and cons of each integration approach:

Integration MethodProsCons
Enterprise Service BusCentralized Integration
Complex Workflows
Single Point of Failure
Limited Extensibility
APIsReal-time Integration
Abstracts Legacy Complexity
API Development Effort
API Versioning
Integration PlatformPre-built Connectors
No-code Approach
Potential Vendor Lock-in
Limited Flexibility
Robotic Process AutomationQuick to Implement
Scalability Issues
Security Limitations

Best Practices for Legacy System Integration

Based on the key pros and cons, here are some recommended best practices:

  • Evaluate business priorities – Focus first on high-value legacy integrations that will maximize ROI.
  • Assess legacy systems suitability – Gauge upgradability, security risks, dependencies before integration.
  • Combine solutions – Blend ESB, APIs, iPaaS and RPA to get best-of-breed integration.
  • Start small, deliver value – Focus on a few high-impact integrations first before expanding.
  • Build APIs for innovation – Expose core legacy functions as APIs to fuel innovation.
  • Address security comprehensively – Secure legacy systems and connections to prevent breaches.
  • Have a sunset roadmap – Define a roadmap to gradually modernize and phase out legacy platforms.

Key Takeaways

  • Integrating legacy systems enables leveraging new innovations while limiting business disruptions.
  • Common techniques include ESB, APIs, iPaaS and RPA – each with pros and cons.
  • Start with high-value integrations first to maximize business impact.
  • Blend multiple solutions like APIs and iPaaS based on use case.
  • Follow security best practices and have a retirement roadmap.

With careful strategy and planning, legacy integration can pave the way for IT modernization in your organization. Reach out if you need help formulating a legacy integration approach tailored to your specific business and technology landscape.

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