iPaaS vs. ESB vs. Two-Way Sync: How To Choose the Right Integration Architecture
When leadership asks for an integration platform, IT usually picks from one of two types of integrations: ESB (enterprise service bus) or iPaaS (integration platform as a service). But while these two approaches are go-tos for a reason, they’re not the only two you should consider. There’s an entire category of integration needs that isn’t met by either of these options; keeping data continuously aligned across tools, rather than just moving it from point A to point B. That’s where a two-way sync platform comes in.
In this guide, you’ll find a framework for determining where each integration architecture excels. It’s not about which one’s the ultimate choice; it’s about which one’s the right choice for what you need.
What ESB still does well
ESB isn’t a legacy relic. It’s mature architecture that still serves a specific purpose. The centralized hub-and-spoke bus gives a single platform for everything else to integrate into. In large, enterprise organizations with dozens (or even hundreds) of systems, this streamlines your integration process tremendously, since everything connects to the same platform. Configuration settings remain relatively consistent, which isn’t the case when you’re managing multiple integration pairs. When you’re integrating complex, on-premise systems, ESB is often still the way to go. It gives you more control over what you’re integrating (and how) without the massive maintenance involved with many other platforms — or inconsistency around which on-premise systems are supported and which ones aren’t.
Another advantage of ESB? Governance and compliance. Integration governance ensures that sensitive data isn’t accessed by unauthorized actors, standardizes configuration, and keeps costs predictable. Having a single, customizable system makes that process much easier. Similarly, ESB naturally creates a more robust audit trail, allowing IT professionals to streamline reviews when things go wrong. For industries with strict regulatory requirements (e.g., finance, healthcare, government), an ESB is often one of a few options that meet these requirements.
Where ESB falls short
While ESB still has its uses, it lags behind other options in a few key areas:
- Cloud-native SaaS integration: Organizations that primarily use cloud-based SaaS tools won’t get as much value out of an ESB platform, especially compared to cloud-native platforms.
- Horizontal scaling: When you use cloud-based integration platforms, resources are automatically added (at a price) as you add more integrations or data volume. With on-premise ESB platforms, you’re upgrading physical infrastructure. That cost quickly becomes prohibitive compared to other solutions.
- Deployment speed: ESB systems take longer to deploy than other options. If you’re going into your integration process prepared to make that investment, then that’s not an issue. But other options don’t require that level of investment.
- Cost of ownership: Hundreds of thousands of dollars. That’s how much you can expect to pay for this kind of infrastructure.
What iPaaS gets right (and what it doesn’t)
This is the dominant modern integration approach for a reason. An iPaaS is cloud-native, meaning you don’t need expensive, on-premise infrastructure. That means these platforms are a smaller investment and involve less maintenance. Pre-built connectors can be deployed in days or weeks instead of needing to be built from scratch over months of IT work.
iPaaS is the leading choice for integrating SaaS tools to each other, integrating them with hybrid cloud environments, managing APIs, and automating workflows. It’s often the first platform organizations try when they don’t have the budget for ESB or other options, and it’s a strong choice for centralized integration. Enterprise iPaaS typically offers a massive ecosystem of prebuilt connectors, meaning you can usually integrate most, if not all of your tool stack with a single platform. It also centralizes integration governance (preventing issues like outdated credentials and configuration inconsistencies), access control, and more. For large organizations, this eliminates shadow IT and duplicated integrations.
That centralization doesn’t just apply to how you use your integrations internally. It also means security patches, uptime, and platform updates are all handled by a vendor, rather than your team. This shifts the operational burden off of internal teams and reduces your total cost of ownership dramatically.
Where iPaaS falls short
iPaaS might be the platform of choice for many, but it still has one main drawback: its core infrastructure. This infrastructure orchestrates complex workflows, but doesn’t support bidirectional data syncing. This can create issues with workflows that need to move data back and forth between the same tools. Issues like latency, conflicts, and infinite loops.
Imagine a support team that works in ServiceNow, collaborating with a development team in Jira whenever a support ticket needs to be escalated. An iPaaS can send that ticket to Jira, creating an equivalent work item. But if you want fields to stay up to date in both tools, you need separate flows for each tool, since each flow only pushes data in one direction. That can lead to teams on either end waiting for updates and additional maintenance to prevent loops and conflicts between integrations.
Two-way sync: A different architecture for a different problem
Two-way sync works on a completely different level than other infrastructure options. A two-way sync platform doesn’t use one-way automations or a centralized hub-and-spoke bus. These tools build two-way relationships between your systems, keeping work items up to date automatically as you work. Imagine, for example, that you have software developers working in Jira and project managers working in Asana. You need work items in Jira to end up in Asana so PMs can properly organize work. A two-way sync tool doesn’t just create Asana tasks to match Jira work items; it also updates due dates, adds comments, and changes custom fields to match the work happening in both tools.
There is no other infrastructure that builds these relationships. An iPaaS pushes information in one direction. An ESB routes everything through a central platform. A platform like Unito allows business users to build no-code integrations to keep a pair of tools in sync as they work. Setup takes minutes, rather than weeks, and deployment doesn’t cost hundreds of thousands of dollars.
Where two-way sync falls short
Some platforms can’t be replaced by a two-way sync. ERP integration is one example of these. Similarly, not all workflows can effectively be managed by a two-way sync platform. Overly complex, multi-step workflows that need deep orchestration often need deeper integrations.
Two-way sync solves a narrow problem deeply, not a broad problem shallowly.
How to choose: A decision framework
When considering different integration architecture, you need to evaluate them for integration depth and breadth, as well as ease of use. Knowing where each type of infrastructure excels — and where it doesn’t — here’s how you choose between them.
When to use ESB
If your use case checks any of the following boxes, use ESB:
- Your integration involves complex on-premise or legacy systems: This is still where ESB excels compared to other options.
- You need strict message handling guarantees: Whether it’s message ordering, guaranteed delivery, or protocol transformation, ESB is often the better choice.
- You have dedicated integration teams and budget: If you can dedicate the man hours and budget to deploying and maintaining an ESB system, then it’s still a worthy choice.
When to use iPaaS
Here’s when you should consider iPaaS instead of other options:
- You’re connecting cloud tools: SaaS applications don’t interact well with ESB and similar systems. If one-way automations are enough, then iPaaS might be the way to go.
- You need API management and prebuilt connectors: Most iPaaS systems have a host of prebuilt connectors that support many use cases, but built-in API management can help you plug the gaps where prebuilt connectors aren’t available.
- You don’t need two-way sync: If your workflows can be managed with trigger-action automations, the iPaaS is a strong choice.
When to use two-way sync
Here’s when two-way sync is the best option by far:
- You want seamless collaboration: Other platforms push data in batches or only in one direction. Two-way sync is the closest you can get to feeling like everyone is working from the same platform.
- You need tools to stay in sync in real-time: No integration architecture keeps tools in sync quite like two-way sync. That maintains data integrity as you work in a way other infrastructure can’t.
- You need democratized access: Two-way sync platforms are more user-friendly than other integration platforms, meaning IT doesn’t have to build every integration. This can help you clear your integration backlog by ensuring you don’t have one in the first place.
How these architectures can coexist
Choosing one type of infrastructure doesn’t mean you have to forego the others. Most organizations use multiple integration platforms to support a variety of workflows. ESB can be the legacy backbone for on-premise and legacy systems, while iPaaS becomes the cloud workflow orchestration layer. Finally, two-way sync is the toolbox of choice for cross-team tool alignment. The key is in matching the right type of infrastructure to what you need.
Imagine a project management workflow that involves on-premise source control and CI/CD infrastructure for work on software development projects, a cloud-based project management tool, and another project management tool for working with contractors. Your ESB might pull in data from dozens of tools to give developers what they need to work, centralizing it in a single system they can work from. From there, an iPaaS might push relevant development tasks to your project management tool, allowing leaders to get visibility on development work for sprint planning and resource management purposes. Finally, a two-way sync solution picks up tasks from your internal project management tool and syncs them to the project management tool used for contractors. That way requirements, comments, and requests are updated in real-time as contractors work.
No one infrastructure is better than the other two. They all have their place. The question, often, isn’t “what do I replace integration tool X with?” but “what do I add to plug the gaps?” If you already have an iPaaS system, you don’t need to replace it. You need to add an ESB if you have significant support gaps for your on-premise systems or two-way sync for addressing tactical collaboration issues, rather than large workflow orchestration. Similarly, you can supplement your ESB with iPaaS for managing cloud-based services broadly or two-way sync when you have teams struggling to move quickly when working across tools.
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FAQ: iPaaS vs. ESB vs. two-way sync
Is ESB dead?
No, ESB (enterprise service bus) isn’t dead, but it’s becoming less relevant. Tools like Red Hat Fuse and IBM App Connect still serve complex on-premise integration needs, but are rarely the go-to choice for cloud architecture. As most organizations move the bulk of their operations to the cloud, ESB platforms aren’t as useful.
Can iPaaS do two-way sync?
Some iPaaS can handle two-way sync, but it’s not the norm. Most iPaaS chain one-way automations to handle complex workflows and simulate two-way sync. But this introduces latency, conflict risks, maintenance overhead, and the risk of infinite loops. Purpose-built two-way sync platforms like Unito prevent these issues natively.
What’s the difference between integration and synchronization?
Synchronization is a type of integration, and not all integrations are synchronization. An integration moves data between systems, whether that’s through automation (pushing data in one direction based on a trigger) or synchronization (maintaining ongoing, bidirectional relationships between two systems).
How long does it take to set up a two-way sync?
Most two-way sync platforms (like Unito) can be set up in minutes. They usually have a drag-and-drop interface, don’t require any code, and offer pre-built connectors you can configure in a few clicks. They have a much quicker deployment time than enterprise iPaaS and similar platforms, which can take weeks or months to properly deploy.
Do I need to replace my iPaaS with a sync platform?
Not necessarily. If you’re already using an iPaaS, it’s likely solving multiple problems already. You need a complementary solution that fixes what your iPaaS doesn’t, not a complete replacement. Keep your iPaaS for workflow orchestration and event-driven automation, and complement it with something like two-way sync for keeping teams aligned between tools.