5 Common Mistakes Developers Make in Outsystems (and How to Avoid Them)

When developers first start working with OutSystems, they’re often amazed by how quickly they can build applications using a low-code platform. With its drag-and-drop features, built-in integrations, and fast deployment — it feels like magic!

But like any powerful tool, OutSystems requires understanding and discipline. Even experienced developers can fall into certain traps that lead to performance issues, scalability problems, or maintainability headaches later on.

In this blog, we’ll look at 5 common mistakes developers make in OutSystems — and how you can avoid them.

Mistake 1: Ignoring Architecture and Reusability

The mistake:Many developers rush to build screens and logic without planning the app’s structure. They copy and paste components instead of creating reusable modules or blocks.

Why it’s a problem:It leads to code duplication, inconsistent behavior, and future maintenance nightmares.

How to avoid it:

• Think modular: break your app into reusable components.

• Use Reusable UI Blocks and Server Actions wherever possible.

• Follow the OutSystems Architecture Canvas (Core, Library, and End-User Modules).

💡 Tip: Always start your project with a solid architecture design — it saves hours later!

Mistake 2: Not Optimizing Aggregates and Queries

The mistake: Developers often use large aggregates without filters or joins that fetch unnecessary data.

Why it’s a problem: It causes slow performance, especially when your app scales or has thousands of records.

How to avoid it:

• Always apply filters before fetching data.

• Use pagination or On Demand Data Fetching.

• Limit your queries to only required fields.

• Regularly check the Execution Plan in Service Studio for performance hints.

💡 Tip: If a screen loads slow, check your aggregate first — it’s usually the culprit.

Mistake 3: Overcomplicating UI and Logic

The mistake: Trying to make the UI too fancy or writing too much client-side logic when OutSystems already provides built-in functionality.

Why it’s a problem: Complex logic on the client side can cause unexpected behaviour, maintenance challenges, and slower rendering.

How to avoid it:

• Use Reactive Patterns instead of writing custom JavaScript.

• Keep your screens simple and consistent with the company’s design system.

• Let the platform handle most of the front-end behaviour.

💡 Tip: Simplicity = performance. The best UIs are intuitive, not overloaded.

Mistake 4: Ignoring Best Practices for Data and Entities

The mistake: Developers often put all entities in one module or skip normalization for speed.

Why it’s a problem: It affects scalability, increases technical debt, and can cause dependency hell later.

How to avoid it:

• Separate Core Data Entities and End-User Entities.

• Use References wisely.

• Don’t expose internal data structures to UI modules directly.

• Follow OutSystems’ recommended Layered Architecture.

💡 Tip: Keep your Core layer clean — that’s where scalability begins.

Mistake 5: Not Following Naming Conventions and Documentation

The mistake: Many developers skip proper naming conventions for screens, variables, or actions — and don’t document their logic.

Why it’s a problem: Your app might work fine today, but when another developer takes over (or you revisit it after 6 months), understanding it becomes painful. Poor naming = confusion, and no documentation = wasted time.

How to avoid it:

• Always follow OutSystems naming standards (for entities, screens, actions, and variables).

• Write brief descriptions for your public actions and components.

• Maintain a simple project documentation — even a one-pager helps new team members onboard faster.

• Use consistent prefixes/suffixes like GetCustomerList, UpdateOrderDetails, etc.

💡 Tip: Code that explains itself is great — but well-named code is even better.

Final Thoughts

Every developer makes mistakes — but what separates the great ones is the willingness to learn and improve.

OutSystems gives you incredible speed and flexibility, but mastering it means combining good technical habits with smart architectural thinking.

So the next time you start a new app, remember:✅ Plan your architecture✅ Optimize your queries✅ Keep your UI simple✅ Structure your data properly✅ Name and document everything clearly

Do this, and you’ll build apps that are faster, cleaner, and easier to scale.

💬 Your Turn

What’s one OutSystems mistake you’ve learned from? Share your experience — your insight might help another developer!