Design question on UI5 applications: 1-tier or 3-tiers?

Hi all,

I'd like to ask for advice on a general design question related to UI5 applications.

I can see two different approaches to development: 1-tier vs 3-tier.

1-tier: the UI5 application directly invokes OData services available on Gateway/PO/etc possibly with the help of a Web Dispatcher to prevent cross-origin issues. This leaves no place to add any server side business logic (e.g. to handle transactions that span multiple systems, error handling, validation and so on). The UI layer must take care of any logic and possibly must integrate data from different data sources.

3-tier (UI/logic/DB): the UI5 application is part of a container application (such as Java EE app) and invokes a local REST api, deployed in the same application. The local REST API hides the server side logic. Local persistence is available and integration with external systems takes place through the business logic layer e.g. through SOAP.

Which approach would be better or recommended?

I'd be grateful if any best practice/experience could be shared on this.

Thanks, regards

Vincenzo