How to Evaluate an OutSystems Migration Partner

You've decided to leave. Now what?

The decision to migrate off OutSystems is rarely impulsive. It comes after months — sometimes years — of escalating license costs, failed negotiations, hiring struggles, and the slow realization that your organization's most critical applications are locked inside a platform you don't control.

By the time you're evaluating migration partners, you've already done the hard part: acknowledging that the current path is unsustainable. But the migration itself introduces a new category of risk. Choose the wrong partner and you'll spend twelve months and a significant budget replacing one problem with another.

The market for OutSystems migration services is small, fragmented, and difficult to evaluate from the outside. Most firms that claim to offer "application modernization" have never opened Service Studio. The ones that have may still be proposing approaches that won't survive contact with your actual codebase.

Here's how to separate the firms that understand what they're doing from the ones that are learning on your budget.

Start with the destination, not the departure

The first question to ask any migration partner isn't about OutSystems. It's about where they're taking you.

Some firms specialize in moving applications from one low-code platform to another — OutSystems to Mendix, OutSystems to Power Platform, OutSystems to ServiceNow. This is a lateral move. You're trading one vendor's lock-in for another's. The licensing model changes, the visual development environment changes, the talent pool changes. The fundamental problem — that you don't own your code and can't leave without rebuilding — stays exactly the same.

If you're migrating to escape vendor dependency, the destination needs to be open, standard technology. That means a modern stack your team can hire for, your CI/CD pipeline can deploy, and your version control system can track. React, Next.js, PostgreSQL, standard cloud infrastructure. Code that any competent developer can read, modify, and maintain without a proprietary IDE.

Ask the partner: what does the target architecture look like? If the answer involves another platform subscription, ask why you're migrating at all.

They need to understand OutSystems from the inside

Enterprise application modernization is a large and established market. Plenty of firms migrate mainframe applications, refactor monoliths into microservices, or move on-premise systems to the cloud. These are legitimate competencies, but they don't automatically translate to OutSystems.

OutSystems applications are architecturally unique. Business logic lives in visual action flows, not source files. Data models are defined through entities that map to database tables in non-obvious ways. Screen logic, server actions, client actions, aggregates, and integration points are all expressed in a proprietary visual language that has no direct equivalent in conventional development.

A partner evaluating your OutSystems application needs to understand this structure natively — not reverse-engineer it during the engagement. Ask them:

How do you assess the complexity of an OutSystems application? A competent partner will talk about entity relationships, server action depth, integration surface area, BPT (Business Process Technology) workflows, and the number of custom Forge components. If they talk about "lines of code" or "screen count" as their primary metric, they're applying conventional measurement to an unconventional platform.

Have you worked with OutSystems O11 Traditional Web, Reactive, and Mobile applications? These are architecturally different. Traditional Web applications compile to .NET server-side rendering. Reactive and Mobile applications use a JavaScript client runtime. A partner who only knows one type may underestimate the complexity of the other.

What do you do with Forge components? OutSystems applications frequently depend on community-built Forge components for functionality that the platform doesn't natively provide. Some of these components are thin wrappers around JavaScript libraries. Others are deeply integrated into the platform's internal APIs. A migration partner needs to know which are which, because the migration path differs significantly.

Automated analysis versus manual guesswork

The traditional approach to legacy migration assessment is straightforward: a team of consultants reviews the application manually, documents the business logic, estimates the rebuild effort, and produces a scoping document. For conventional applications — where you can read the source code in a text editor — this works reasonably well.

For OutSystems, manual assessment is dangerously unreliable.

The visual development model means that complexity hides in places human reviewers consistently miss. A server action that appears simple in Service Studio may contain deeply nested logic across multiple referenced actions. An entity model that looks clean at the top level may have implicit dependencies, calculated attributes, and delete rules that only reveal themselves at migration time. Integration points may reference environment-specific configurations that aren't visible in the application itself.

The partners who produce the most accurate assessments use automated tooling to analyze OutSystems applications systematically. They can quantify the number of entities, actions, screens, and integration points programmatically — not because automation replaces human judgment, but because it ensures nothing gets missed.

Ask any prospective partner: how do you handle the gap between what's visible in Service Studio and what actually exists in the application? If the answer is "our senior consultants are very experienced," that's not a methodology. That's a hope.

The detach question

Any competent partner will have a clear position on OutSystems Detach — the platform's built-in feature for exporting application source code. If they suggest using Detach as the starting point for migration, that's a red flag.

Detach produces .NET source code that technically compiles but practically requires near-complete rewriting. The generated code contains deep dependencies on OutSystems runtime libraries, uses machine-generated variable names, and follows architectural patterns that no developer would choose voluntarily. Teams that start from Detach output typically spend more time understanding and cleaning the generated code than they would have spent rebuilding from a clean specification.

The right partner will tell you this directly. They won't position Detach as a shortcut, because it isn't one. If anything, it's a detour that costs time and creates false confidence.

For a deeper look at what Detach actually produces, see our complete guide to the OutSystems Detach process.

Phased migration, not big-bang replacement

Any migration partner proposing to migrate all of your OutSystems applications simultaneously is either very brave or very inexperienced. For organizations with more than a handful of applications, phased migration is the only approach that manages risk responsibly.

A phased approach typically starts with one application — ideally one that's important enough to demonstrate value but contained enough to limit blast radius if something goes wrong. The first application validates the partner's methodology, surfaces unexpected complexity, and produces a working reference that subsequent migrations can follow.

Ask the partner to describe their phased approach in concrete terms:

How do you select the first application? Good answers involve criteria like integration surface area, business criticality, user base size, and technical complexity. The goal is to find an application that's representative without being the most complex thing in the portfolio.

What happens to the OutSystems applications that aren't being migrated yet? During a phased migration, your organization will run both OutSystems and modern applications simultaneously. The partner should have a clear plan for integration between the two environments during the transition period. If they assume you can simply turn off OutSystems after phase one, they haven't worked with enterprise portfolios before.

What does "done" look like for a single application? This should include not just a functioning application, but deployed infrastructure, CI/CD pipelines, automated tests, documentation, and a handoff process that enables your team to maintain it independently. If "done" means "we hand you a code repository," that's not done.

Data migration deserves its own conversation

Data migration is where OutSystems engagements get complicated and where inexperienced partners get burned.

If your applications run on OutSystems Cloud, you may not have direct database access at all. The partner needs to know how to extract data through the platform's APIs or negotiate database access with OutSystems as part of the transition.

If you're self-hosted, the database is accessible but the schema is not straightforward. OutSystems entities map to tables with platform-generated names and columns. Relationships that appear clean in the entity model may involve surrogate keys, soft deletes, and platform-managed metadata columns that need careful handling during migration.

Ask the partner: have you migrated data from OutSystems databases before, and what specific challenges did you encounter? Generic answers about "ETL pipelines" suggest they haven't. Specific answers about entity-to-table mapping, BPT state data, and audit trail preservation suggest they have.

For more detail on what OutSystems data migration actually involves, see our piece on what happens to your data when you leave OutSystems.

What to ask about your team

Migration doesn't end when the code is deployed. Your team needs to maintain, extend, and operate the migrated applications going forward. A good partner thinks about this from day one.

Knowledge transfer: How will the partner ensure your team understands the migrated codebase? This should go beyond documentation. Pair programming sessions during migration, architecture walkthroughs, and guided handoff periods are standard practice for partners who've done this before.

Existing OutSystems developers: If you have in-house OutSystems developers, the partner should have a perspective on how to involve them in the migration and transition their skills. OutSystems developers understand the business domain better than anyone — that knowledge is irreplaceable, even if the technology stack changes. Partners who dismiss your existing team as "low-code developers who need retraining" are missing the point. The domain knowledge matters more than the syntax.

Post-migration support: What happens in the three to six months after handoff? Issues will surface. Business requirements will change. Your team will have questions. A partner that offers a clean break at delivery is optimizing for their timeline, not your success.

Red flags

Certain patterns should prompt you to reconsider — or at least dig deeper.

"We'll rewrite everything from scratch." This suggests the partner doesn't have a methodology for understanding the existing application systematically. Rewriting from scratch means re-discovering business logic through interviews and manual review, which is slow, expensive, and prone to gaps.

"Our team includes OutSystems-certified developers." Certification demonstrates familiarity with the platform but says nothing about migration capability. Building OutSystems applications and migrating them to modern code are fundamentally different skills.

"We've modernized hundreds of legacy applications." Experience with COBOL, Oracle Forms, or Java EE modernization doesn't transfer directly to OutSystems. The architecture is different, the data model is different, and the extraction challenges are different. Ask specifically about OutSystems engagements — not legacy modernization in general.

Vague timelines with generous buffers. If a partner can't estimate the migration timeline with reasonable precision after analyzing your application, they're probably estimating based on experience with different types of projects. OutSystems migration timelines should be driven by measurable factors: entity count, action complexity, integration surface area, screen count. If the estimate feels like a guess, it probably is one.

No mention of testing. The migrated application needs to produce the same outputs as the original for the same inputs. Partners who don't have an explicit testing strategy — including how they validate business logic equivalence — are leaving correctness to chance.

The assessment is the audition

Most reputable migration partners offer an initial assessment — a scoped analysis of one or two applications that produces a complexity report, a migration plan, and a cost estimate. This assessment is both a deliverable and an audition.

Pay attention to the quality of the assessment itself. Does the report demonstrate genuine understanding of your application's architecture, or does it read like a template with your company name inserted? Does the partner ask sharp, specific questions about your business logic, or do they rely entirely on what they can see in Service Studio?

The assessment should tell you something about your application that you didn't already know. If it doesn't, the partner is operating at the surface level — and your migration will reflect that.

If you're ready to see what an assessment looks like, start a conversation with us. We'll analyze your application and show you exactly what a migration involves — scope, timeline, and target architecture — before you commit to anything.