Agency, iPaaS or Custom Development: Three Paths to CRM Integration Compared

Imagine a mid-sized company: 500 employees, HubSpot as CRM, SAP as ERP. Sales maintains customer data in HubSpot. Finance needs the same data in SAP. And in between? An Excel export that someone triggers manually once a week. It is the classic scenario: two systems, no bridge, plenty of frustration.

Integration is needed. But how? In practice, there are three typical paths companies take. The agency that implements the project. The integration platform that runs as an ongoing service. Or the development team that builds a custom solution. Each of these paths has its own logic, its own costs and its own consequences that only become visible after go-live.

The tricky part: the decision feels purely operational at the start. Which option is fastest? Which is cheapest? But anyone who only looks at the project kickoff overlooks what comes next: maintenance, API changes, staff turnover, growing requirements. The real costs of a CRM integration arise not during setup but in ongoing operations. According to McKinsey, maintenance costs typically account for 15 to 25 percent of initial development costs, and that is every single year.

The agency path is the most intuitive. You have a problem, you bring in someone to solve it. An agency brings expertise: consultants who know HubSpot and SAP, developers who can work with APIs, project managers who keep the timeline on track. The advantage is obvious: you do not have to deal with the technical details yourself.

But that is precisely where the problem lies. What you get is a project, not a continuously operated infrastructure. The agency builds the bridge, hands over the keys and moves on to the next client. The interface works as long as nothing changes. And in practice, something always changes: SAP releases an update, HubSpot extends its data model, the business unit needs a new field.

Every adjustment then requires a new agency ticket. Often the agency builds on its own middleware, such as Azure Logic Apps or a custom scripting solution. That means you have a dependency not only on the agency but also on their technical stack. If the agency closes the project or changes its business model, you are left with a solution that nobody in-house understands, and that may be running on infrastructure you never wanted in the first place.

Agencies are strong when it comes to one-off implementations with a clear scope. But CRM integrations are not one-off projects. They are living connections that evolve with your business. The agency solution is like a bespoke suit: it fits perfectly on the day of delivery. Whether it still fits in two years is another matter entirely.

The second path leads through an integration platform: an iPaaS (Integration Platform as a Service). Instead of commissioning a project, you rent a continuously operated platform that connects systems, orchestrates data flows and includes monitoring out of the box. The crucial difference from the agency: the platform stays. It is not a one-time solution but an infrastructure that grows with your requirements.

Good iPaaS solutions come with pre-configured adapters for common systems that significantly shorten time-to-value. On top of that, they offer visual interfaces for mapping and field rules, real-time synchronization, logs and alerts. The in-house team can make changes themselves without having to engage a service provider every time. A point that mid-market companies particularly value: independence.

However, not every iPaaS is the same. The market now includes over 270 providers, and the range extends from generic toolkit-style tools to specialized platforms. A generic iPaaS can do many things a little but rarely anything really well. Anyone who needs to map complex business rules between CRM and ERP, for example, quickly hits the limits of toolkit solutions. The difference lies in depth: Can the platform handle bidirectional synchronization with conflict detection? Does it support deduplication and golden records? Does it run GDPR-compliant on EU servers? These questions, as we also explore in the comparison of native connectors and iPaaS, separate usable solutions from strategically valuable ones.

Ongoing costs with an iPaaS are transparent and predictable. That is an advantage over the agency, where every change triggers a new quote, and over custom development, where the true costs often only become visible after months.

The third path is the most tempting and the most dangerous: custom development. The promise sounds compelling. Maximum control, no dependency on third-party providers, a solution tailored precisely to your requirements. In theory, that is true. In practice, things look different.

Custom development ties up developer resources permanently. Not just for the build but above all for maintenance. APIs change, authentication protocols get updated, new fields are added. Every one of these changes requires intervention from someone who knows the system. And that is exactly where the biggest risk lies: the knowledge risk when staff leave. If the developer who built the interface leaves the company, the team is left facing a black box. The documentation? Incomplete. The monitoring? Non-existent. Troubleshooting? An adventure.

Maintenance costs for custom development are systematically underestimated. In practice, companies need to budget 15 to 30 percent of the original development costs annually for ongoing maintenance. For complex on-premises systems, maintenance can even account for 70 to 90 percent of total costs over the lifetime. On top of that, custom developments have no built-in monitoring, no retry logic, no alerting. All of that must be built and maintained separately.

There are cases where custom development makes sense: very specific requirements that no iPaaS covers, or regulatory mandates that require a proprietary stack. But for standard scenarios like CRM-ERP integration, that is rarely the case. The desire for control is often confused with independence. Yet a self-built interface that only two people in the company understand is the opposite of independence: it is a risk to your data quality and your ability to act.

The choice between agency, iPaaS and custom development can be structured along six criteria: time-to-value, ongoing costs, dependency, scalability, maintenance effort and compliance.

Time-to-value: The agency delivers quickly as long as the scope is clear. The iPaaS is also rapidly productive thanks to pre-configured adapters, often in weeks rather than months. Custom development takes the longest because everything must be built from scratch.

Ongoing costs: With an iPaaS, they are predictable and transparent. With an agency, you pay per change. With custom development, the initial costs are often lower than expected, but ongoing costs rise with every API change, every new field and every staff change.

Dependency: The agency creates personnel dependency. Custom development creates internal dependency on individual knowledge holders. The iPaaS minimizes both because the platform is standardized and the know-how is based on documented configurations, not on individual code.

Scalability: Connecting new systems, setting up new data flows, implementing additional use cases: this is where the iPaaS plays to its strengths. With an agency, every extension requires a new project. With custom development, technical debt grows with every new connection.

Maintenance effort: With an iPaaS, infrastructure maintenance lies with the provider. Agency solutions require external support for every adjustment. Custom developments tie up internal resources permanently, often developers who should actually be working on strategic topics.

Compliance: EU hosting, GDPR compliance and certifications such as ISO 27001 are built in from the start with specialized iPaaS providers. With custom development and agency projects, compliance must be ensured and demonstrated separately.

The rule of thumb: an agency is suited for clearly scoped one-off projects with no long-term scaling plan. Custom development only pays off for genuine edge cases that no platform covers. For most mid-market companies with growing integration requirements, the iPaaS is the strategically right path. In practice, many companies end up with an iPaaS, often after a detour through agency or custom development.

The iPaaS market is growing rapidly. According to Gartner, the global iPaaS market reached a volume of 8.5 billion US dollars in 2024, with growth of over 23 percent year-on-year. The growth is no coincidence: companies are recognizing that integration is not a one-off project but a permanent infrastructure decision.

At the same time, the gap between generic platforms and specialized solutions is becoming ever more visible. Generic iPaaS tools can connect many systems superficially but fail at the depth that complex CRM-ERP scenarios require. Anyone who seriously wants to map business rules, ensure data quality and demonstrate compliance needs more than a visual flow builder with a hundred pre-configured connectors. This is especially true in the DACH market, where GDPR compliance and EU hosting are not optional but mandatory.

On top of that, poor data quality is expensive. According to Gartner, companies lose an average of 12.9 million US dollars per year due to poor data quality. A large portion of these costs stems from missing or poorly implemented integrations: duplicates, outdated records, inconsistent customer data across system boundaries. CRM integration is therefore not just an IT topic but a direct lever for business success.

This is exactly where MARINI positions itself as a platform: not as a generic toolkit, not as an agency, but as a specialized solution for Customer Intelligence. The MARINI platform connects CRM, ERP and marketing systems bidirectionally and in real time, via a no-code interface that business departments can use independently. Monitoring, logs and alerts are integrated, no separate setup required.

What distinguishes MARINI from generic iPaaS solutions is the depth: complex mappings between HubSpot and SAP, deduplication, golden records, data enrichment and AI-powered classification are part of the Data Cloud, not optional add-on modules. For companies that need more than a data pipeline, namely clean, enriched and usable customer data, that is the decisive difference.

And for everyone who needs support with implementation, MARINI offers Professional Services: a team that helps with setup without disappearing afterwards. Unlike a classic agency model, the platform stays with the customer, along with the know-how, the documentation and the ability to continue working independently. For services within the connected systems, such as HubSpot configuration or SAP customizing, MARINI refers to its partner network.

The decision between agency, iPaaS and custom development is at its core a make-or-buy decision. And as with every make-or-buy decision, it is not just about the price on the day of the decision but about the total cost over the lifetime.

An integration project is not a software purchase that you make once and then forget. It is the beginning of a lasting relationship with your system landscape. If you leave that relationship to an agency, you give up control. If you build it yourself, you almost always underestimate the effort. If you choose a specialized platform, you invest in independence, scalability and predictable costs.

Experience shows that many companies start with the agency because it is the fastest path to a first result. Some build a custom solution in parallel because they do not want to become dependent. And almost all of them end up with an integration platform because they realize that data flows between CRM, ERP and marketing are not a one-off project but an ongoing process that requires an ongoing solution.

The best time to make the right decision is before you have made the wrong one. The second best time is now.