Introduction
IT leaders often face a difficult decision: build integrations in-house for full control, or purchase a middleware platform from a vendor to move faster. We believe you should have the best of both worlds.
On one hand, fully custom development offers freedom and control, but often results in long development cycles, supplemental workflows to ensure documentation stays up to date, and numerous obstacles that come from building integration infrastructure from scratch, such as institutional knowledge loss. On the other hand, legacy middleware platforms provide helpful tools and robust runtime infrastructure, but impose proprietary languages, require niche skills, and come at a high price.
It’s a tough choice. Make the wrong call, and you either end up pouring time and resources into maintaining an internal integration platform rather than driving innovation or renting your own logic back from a vendor.
PolyAPI gives you the best of both worlds. It’s a developer-first platform for building and managing integrations, all while using your favorite development and operations tools. Poly provides you the missing pieces of the development stack optimized for integrations, such as auto-generated SDKs so developers can work with APIs using typed functions in their native language, an AI assistant to speed up discovery of functions from your catalog and code development, and a growing catalog of reusable out-of the box API functions for core enterprise systems – helping teams ship faster, encapsulate best practices, and reduce repetitive work. Everything runs on scalable, serverless infrastructure powered by Kubernetes and Knative, so integrations scale automatically and incur no cost when idle. And if you want a faster path to value, Poly’s expert Solutions Engineering team can partner with your team to help you develop the integrations your business needs.
Homegrown Solutions
Many teams choose to build their own integration platform in-house, often to avoid the cost and constraints of legacy middleware. At first, this approach offers maximum control. Developers work in their own language, deploy to familiar infrastructure, and tailor everything to fit their stack. This approach is widely popular with internal technical teams, because it offers the allure of an exciting new project.
But over time, a custom-built integration platform can become a burden to maintain and operate. Without standardized patterns, reusable functions, or centralized documentation, each new project requires just as much effort as the last. This makes it hard to scale delivery as demand grows. Institutional knowledge in the minds of a few becomes the glue holding everything together, making the system fragile and slowing down development. Losing this institutional knowledge can be catastrophic. Onboarding new engineers becomes hard because they have to be trained on this proprietary stack. What starts as an exciting and fast path to flexibility can quickly turn into a bottleneck and a massive drain on budgets.
Why Do Homegrown Solutions Slow Development?
- Own the full infrastructure burden. You’re responsible for hosting, scaling, and securing your own integration runtime.
- Inconsistent developer experience. Without shared tooling or standards, every integration is built differently and development is slow. Debugging, onboarding, and reuse all become harder over time. This is further exacerbated if multiple different contracting companies are used over time.
- Outdated or missing documentation. Docs often live in wikis or in someone’s head, not in code and are not property cataloged. When teams change, context is lost and integrations become fragile and error-prone.
- Reinventing the wheel. Teams spend time building internal tools for tasks like a microservices deployment pipeline, source code integration, SDK generation, job scheduling, secrets management, and more – reducing the capacity allocated to implementing business critical integrations.
The result: A system that gives you control, but becomes a maintenance burden that slows down delivery, increases operational risk, and creates a massive drain on budgets. At Poly, we’ve seen internal integration efforts balloon into teams of 8 to 50 engineers, costing millions per year just to keep things running, only to eventually get abandoned.
Legacy Middleware
Over the past decade, the rise of integration platforms marked a significant step forward in how enterprises connect their systems. Platforms like MuleSoft, Boomi, and Workato replaced point-to-point connections with drag-and-drop UIs, reusable connectors, and a centralized place to run and manage integrations. These platforms made projects faster to deliver and easier to manage, especially for those involving commonly used systems like Salesforce, SAP, ServiceNow, and Oracle products.
The impact of the first wave of middleware is reflected in the rapid growth of the integration platform as a service (iPaaS) market. According to Gartner, iPaaS revenue climbed from $5.9 billion in 2022 to $7.8 billion in 2023, and surpassed $9 billion in 2024. Gartner projects the market will more than double by 2028, an indication of just how central integration has become to modern IT strategy.
But iPaaS revenue alone doesn’t tell the full story of the cost and complexity enterprises face when dealing with integrations. In parallel, the larger market of systems integrators (SI) has continued to grow, highlighting the ongoing need for professional services to implement, migrate, and integrate systems, even when integration platforms are available to help. IDC estimated that enterprises spent $153.8 billion on software-related systems integration services in 2024, with that number projected to reach $183.4 billion by 2027.
The scale of the SI market underscores a stark reality: while legacy middleware platforms delivered meaningful efficiency gains, they haven’t kept pace with the growing complexity and volume of enterprise integration needs. And this demand isn’t slowing down. As systems become more specialized and customization becomes the norm, enterprises need technologies that are better equipped to handle the innovation they want to deliver.
Where Has Legacy Middleware Fallen Short?
- Work inside proprietary platforms. You don’t work in your preferred native language or IDE, introducing inferior tools and languages supported by proprietary vendors instead of the top most powerful ecosystems of open source.
- Smaller, more expensive labor pool. Proprietary platforms require specialized expertise, limiting who can build and maintain integrations and increasing the cost of staffing and support.
- Hit the ceiling fast. Prebuilt connectors and drag-and-drop interfaces work for simple use cases but break down with real complexity. Customization often means bringing in expensive specialists.
- Costs grow over time. The more you build, the more you pay – not just in license and usage fees, but also in specialized SI engagements and maintenance. For many companies, these costs become unsustainable over time.
- Rigid scalability models. Legacy platforms rely on fixed infrastructure or usage tiers, leading to over-provisioning, performance bottlenecks, and idle costs.
- Hard to support multi-tenant integration use cases. Supporting different schemas, credentials, or workflows for each tenant often requires duplicating flows and creating fragile logic or custom workarounds.
- Vendor lock-in. Logic, flows, and orchestrations live inside the vendor’s platform. You own the code, but you can’t take it with you if you move to a different system.
The result: A solution that starts fast but becomes unsustainably expensive, inflexible, and hard to scale – locking your core business workflows into infrastructure you can’t easily evolve or exit.
Modern Middleware
Modern Middleware, offered by PolyAPI, is not just about incrementally better tooling. It is about redefining the model of how enterprise integrations should be done, with better efficiency, freedom, and cost. Poly gives you full control – use your preferred open source tools and own everything you create, while leveraging our platform as a service to give you the operational capabilities typically provided by middleware platforms.
How Is Modern Middleware Different?
- Build where you’re comfortable. Write integrations in TypeScript, Python, or Java in your IDE of choice. Poly comes pre-trained on ~10,000 functions from enterprise APIs and offers a full ecosystem of libraries and SDKs in those languages, all available directly in your IDE.
- Engage a larger talent pool. Developers can onboard quickly using familiar tooling. No certifications, no proprietary language learning curve. If you want a faster path to value, our Solutions Engineering team can help deploy and operationalize it with you.
- Accelerate development with AI. Prompt Poly or GitHub Copilot in any human language to find and use APIs and event handlers within your catalog. And as you build, Poly automatically adds your new functions, webhooks, and snippets to your catalogue.
- Automatically catalog your APIs. Poly captures and organizes your API endpoints and custom functions, whether imported via OpenAPI, observed from Postman, or cataloged at deploy time, creating a centralized, discoverable integration layer.
- Generate native SDKs automatically. From your catalog, Poly auto-generates SDKs in TypeScript, Python, and Java, giving developers instantly usable functions with built-in auth, error handling, and autocomplete, so they can build faster, reduce bugs, and stay consistent across teams.
- Choose where it runs. Poly runs on Kubernetes, uses Knative for serverless scaling, and supports both self-hosted and fully managed deployments. What you build can run anywhere: your laptop, your servers, your cloud, or our platform.
- Enhance security and permissions. Poly integrates with HashiCorp Vault and other popular vault providers to store and manage secrets securely. Credentials are injected at runtime, never exposed in integration runtime logs or memory, and management rights can be permissioned.
- Own what you build. Your microservices and orchestrations are written in native TypeScript, Python, or Java and versioned in your own repositories. You’re not renting functionality or writing code which only runs on a third party platform. You’re building assets your team owns and can choose to self-host in the future.
The result: Enterprise integrations delivered faster, with lower cost, no lock-in, and code your team fully owns. All built on top of the best open technologies that your developers already know and love.
Conclusion
Middleware should not be a tax on growth. It should accelerate delivery, reduce friction, and give your team full control over how integrations are built, maintained, and scaled. The first wave of integration platforms helped enterprises move faster, but at a cost: proprietary languages, rigid tooling, and long-term lock-in. Our mission at Poly is to enable you to offload the complexity of integrations so that you can focus on your mission.
PolyAPI accelerates integration timelines by 5X, while lowering total cost through increased developer throughput, fewer external dependencies, and infrastructure that scales efficiently. It helps your team deliver faster without increasing overhead, and turns integration from a sunk cost into a durable, reusable asset you own. Want to see Poly in action? Check out our growing list of case studies.
Ready to take ownership of your integration layer? Talk to the PolyAPI team to see how Modern Middleware can accelerate your roadmap or learn more about common use cases built on Poly.