Demystifying SAP BTP: Everything You Need to Know

I. Introduction to SAP BTP

What is SAP BTP?

Definition and purpose

SAP BTP (Business Technology Platform): It’s a platform that incorporates a collection of cloud-based tools and services from SAP that helps businesses build, deploy and manage applications.

The main purposes of SAP BTP are:

1. Application Development and Extension: BTP offers tools and environments like Cloud Foundry and ABAP Environment, allowing developers to build new cloud-native applications or extend existing SAP solutions.

-??????? Cloud Foundry: A platform within SAP BTP that allows developers to use various programming languages and frameworks to build applications.

-??????? ABAP Environment: A specific environment within SAP BTP designed for building and extending applications using the ABAP programming language, often used with SAP's classic business software.

2. Integration: The platform provides services for connecting different systems and applications, enabling seamless data flow between various business processes.

3. Automation: Enables organizations to streamline repetitive tasks, improve efficiency, and reduce manual intervention in business processes. This could include SAP Build Process Automation for automating routine tasks such as data entry or invoice processing. SAP BTP also offers workflow automation capabilities, allowing organizations to design, execute, and monitor complex business workflows with ease.

4. Data Management and Analytics: BTP includes solutions like SAP Analytics Cloud, SAP HANA Cloud and SAP Datasphere that enable businesses to manage, analyse, and gain insights from their data.

-??????? SAP Analytics Cloud currently offers several means for analyzing, reporting, and summarizing data like, for example, the Analytics Hubs, the Digital Boardroom, Smart Insighst, Smart Predict, and more. You can automatically gain insight from any level of detail with augmented analytics features powered by artificial intelligence and machine learning technology. Accelerate growth by automatically discovering the key influencers of past results to simulate future scenarios and predict outcomes.

-??????? SAP HANA Cloud: is a fully managed in-memory multi-tier cloud database as a service (DBaaS). As the cloud-based data foundation for SAP Business Technology Platform, SAP HANA Cloud integrates data from across the enterprise, enabling faster decisions based on live data. SAP HANA Cloud is one of the four pillars of the SAP Business Technology Platform and provides the data services to handle constantly growing data volumes in a central place.

-??????? SAP Datasphere is a cloud-based data management solution that helps organizations integrate, manage, and analyze data across SAP and non-SAP systems. It allows businesses to create a unified data foundation by connecting disparate data sources, enabling seamless data access, cataloging, and virtualization. This helps organizations streamline data processes, improve data quality, and make data-driven decisions with real-time insights.

5. Innovation and Agility: BTP facilitates rapid development and deployment of applications, fostering innovation and enabling businesses to adapt quickly to changing market demands.

6. Artificial Intelligence (AI): SAP BTP offers a comprehensive set of AI technologies and services, for example SAP AI Business Services and Generative AI Hub.

Overall, SAP BTP acts as a comprehensive platform that helps businesses transform their digital landscape by leveraging cloud technologies, data-driven insights, and agile development methodologies.

II. Architecture and Services

Introduce SAP BTP Commercial Models:

1.???? Pay-As-You-Go (PAYG)

This commercial model lets you sign up to start using cloud services in your production environment with no upfront cost, no minimum usage requirements, and no financial commitments. You can easily start with this commercial model through the SAP Store.

What does this mean?

• Pay-As-You-Go for SAP BTP allows you to build applications in your production environment and pay only for what you use.
• You can start small, build productive apps, and convert to SAP BTP Enterprise Agreement (BTPEA) once you have achieved predictable usage.
• With no minimum usage requirements, you can avoid over-provisioning
• Access to free tier service plans to try out services without any costs within your productive environment
• Available services for this commercial model: https://discovery-center.cloud.sap/serviceCatalog?commercialModel=payg&provider=all&regions=all

2.???? SAP BTP Enterprise Agreement (BTPEA)

SAP BTPEA (SAP BTP Enterprise Agreement) is a commercial model that allows for the consumption of cloud credits based on actual usage. These cloud credits get paid upfront like a pre-paid model

What does this mean?

• Get access to all services available under BTPEA and configure them in your global account with just one contract. This includes new features or innovations available after the contract signing date
• Consume services based on project requirements, without having to change your contract, and only get charged for what is used
• Access to free tier service plans to try out services without any costs within your productive environment
• Available services for this commercial model.

3.???? Subscription

This commercial model lets you choose a fixed set of services for a fixed rate, regardless of actual consumption.

What does this mean?

• The contract includes the exact services you can use in your project and will be provisioned in your global account for entitlements
• The entitled cloud services can be used up to the limit of your purchased subscription. To use more, you can increase your license volume
• Available services for this commercial model

Architecture of SAP BTP

1.???? Global Accounts

A global account is the realization of a contract you made with SAP. A global account is used to manage directories, subaccounts, members, entitlements, and quotas. You receive entitlements and quotas to use platform resources per global account and then distribute the entitlements and quotas to the subaccount for actual consumption.

?2.???? Directory

Directories allow you to organize and manage your subaccounts according to your technical and business needs. A directory can contain directories and subaccounts to create a hierarchy. Using directories to group other directories and subaccounts is optional - you can still create subaccounts directly under your global account

3.???? Subaccounts?

Subaccounts let you structure a global account according to your organization's and project's requirements with regard to members, authorizations, and entitlements. A global account can contain one or more subaccounts in which you deploy applications, use services, and manage your subscriptions. Subaccounts in a global account are independent of each other. This is important to consider with respect to security, member management, data management, data migration, integration, and so on when you plan your landscape and overall architecture.

Each subaccount is associated with a region, which is the physical location where applications, data, or services are hosted. The specific region is relevant when you deploy applications and access the SAP BTP cockpit using the corresponding cockpit URL. The region assigned to your subaccount doesn't have to be directly related to your location. You could be located in the United States, for example, but operate your subaccount in Europe.

The entitlements and quotas that have been purchased for a global account have to be assigned to the individual subaccounts.

A quota represents the numeric quantity that defines the maximum allowed consumption of a resource. In other words, how much of a service plan you're entitled to use.

4.???? Entitlements

An entitlement is your right to provision and consume a resource. In other words, entitlements are the service plans that you're entitled to use. You could also say an entitlement is a booked option or are the booked services you can use in your SAP BTP global account.

Environments constitute the actual Platform as a Service offering of SAP BTP that allows for the development and administration of business applications. Environments are anchored in SAP BTP on the subaccount level.

Each environment comes equipped with specific tools, technologies, and runtimes that you need to build applications. So a multi-environment subaccount is your single address to host a variety of applications and offer diverse development options. One advantage of using different environments in one subaccount is that you only need to manage users, authorizations, and entitlements once per subaccount, and thus, grant more flexibility to your developers.

Environments for Your Applications

Cloud Foundry Environment

The Cloud Foundry environment allows you to create cloud applications. Cloud Foundry (CF) is an open-source cloud native platform as a service (PaaS), which comprises a set of specifications and tools around the whole application development lifecycle. This includes application deployment, application lifecycle management, service dependency management, security, and more. For interaction, Cloud Foundry offers a command line interface (CF CLI), which allows for high automation through scripting. You can build your application on open standards with Java, Node.js, and Python build packs provided by SAP. Alternatively, bring other languages with community build packs for PHP, Ruby or Go.

KYMA Environment

The Kyma environment provides a fully managed Kubernetes runtime based on the open source project "Kyma". Kubernetes, similar to Cloud Foundry, is an open-source cloud native platform for managing the application lifecycle. In contrast to CF, it has a larger focus on containers, container orchestration, and scalability. Kyma allows developers to extend SAP solutions with serverless functions and combine them with containerized microservices. You can also use the Kyma environment to deploy microservices or even build full-stack applications.

ABAP Environment

The ABAP environment is mainly targeted at creating extension applications for ABAP based products, such as SAP S/4HANA Cloud, but also lets you develop independent cloud applications. Technically, the ABAP environment is a cloud enabled environment which lives within the Cloud Foundry or the Kyma environment. The ABAP environment is based on the latest ABAP platform cloud release that is also used for SAP S/4HANA Cloud. The software stack contains standard technology components that are familiar from the standalone Application Server ABAP. The ABAP environment supports the ABAP RESTful Application Programming Model (RAP) including SAP Fiori and Core Data Services (CDS).

5.???? Regions

You can deploy applications in different regions. Each region represents a geographical location (for example, Europe, US East) where applications, data, or services are hosted. A region is chosen at the subaccount level. For each subaccount, you select exactly one region. The selection of a region is dependent on many factors: for example, application performance (response time, latency) can be optimized by selecting a region close to the user. The global account itself is also running in a region.

SAP BTP Cockpit

The SAP BTP cockpit is the central user interface for administering and managing your SAP BTP accounts as a platform user. To access the SAP BTP cockpit, you need to open a specific URL: https://.cockpit.btp.cloud.sap. You can replace the region with the one you are operating in (for example: eu10, us10, ap10) to have a lower response time and latency to the cockpit.

Account Explorer

After choosing the global account you want to access with the SAP BTP cockpit, you get forwarded to the Account Explorer. The Account Explorer displays all directories and subaccounts inside of the global account. From this point on, you can navigate into the subaccounts or directories by simply choosing them. The Account Explorer is not only for navigating between the subaccounts or directories – inside of the Account Explorer you can also create, delete, or move subaccounts or directories.

Subaccount Overview

On this page, you can see the configured entitlements of the subacccount and a lot of other important identifiers and information, like the region and provider of the subaccount, the subdomain, the tenant ID, and the subaccount ID. These IDs are relevant for some scenarios like, for example, connecting a Cloud Connector or opening an incident in case of issues with the subaccount. Over the menu, you can navigate to the capabilities and settings of the subaccount like, for example, accessing the Service Markeplace to create instances and subscriptions from services inside of the subaccount. You can access the entitlements to change them and enhance the subaccount in this way.

When you want to manage a user's permissions and authorizations for the subaccount itself, or for capabilities running inside of this subaccount, you can navigate to the Security area. You can also access the Usage Analytics to get some metrics and diagrams from the subaccount.

Service Marketplace

When you want to create a service instance or a service subscription, you can do that through the Service Marketplace. Inside of the Service Marketplace, you get everything displayed with details and descriptions of what you can use inside of your subaccount based on the entitlements you've set.

You can access instances and subscriptions you've already created through the menu entry Services → Instances and Subscriptions. There are also other ways to create instances and subscriptions including tools outside of the SAP BTP cockpit.

If you need more assistance in working with the SAP BTP cockpit, you can consult the official product documentation.

?

Services in SAP BTP

The Services Types in SAP BTP

1.???? Instance

A service instance is a set of capabilities which get consumed via API's and/or bindings. Some services also require an additional environment like Cloud Foundry or Kyma to work properly. Depending on the service, you can also utilize a graphical application, in this case, definitely an additional environment is required because service instances don't have their own runtime built in.

2.???? Subscription

A service subscription is standalone and runs without the need of an additional runtime environment or any other service. These services mostly come with an application you can open and use.

Connectivity in SAP BTP

The SAP Connectivity service provides a connectivity proxy that can be used to access on-premise resources through a Cloud Connector. With SAP Destination service, you can retrieve and store the technical information about the target resource (destination) that you need to connect your application to a remote service or system (internet or cloud connector).

What is the Cloud Connector?

The Cloud Connector connects SAP on-premise back-ends (or even supported non-SAP systems) to SAP BTP subaccounts via an encrypted tunnel. The connection is bidirectional. From an architectural point of view, the Cloud Connector is a possible single point of failure. For this purpose, there is also the possibility of high availability, monitoring, alerting, and more.

In principle, there are two types of connections to and from the SAP BTP:

• Internet Connectivity. (is needed when you want to consume capabilities or data from a resource on the internet)
• Cloud to On-Premise Connectivity (or other way around) (is used when you want to utilize your existing on-premise landscape resources)

III. Application Development and Automation

SAP Build Components

SAP Build allows for integration with both SAP and non-SAP apps and systems.

SAP Build consists of three components to create no-code based projects:

SAP Build Apps

With drag-and-drop functionality, it is possible to build UIs with a consistently updated component-library without any developer experience. Furthermore, it is possible to create any logic with visual flow functions and to have the opportunity to use individual style properties and advanced theming support, by which a clear development and user experience is provided with your created apps running on web, iOS, Android, and native runtime optimized for each platform.

It is easy to access and bind your data and other data to the user interface due to OData APIs and REST APIs.Develop apps with SAP build apps using drag and drop simplicity.

SAP Build Process Automation

Enables organizations and companies to manage the automation of workflows and processes using visual features. All advanced workflow management capabilities like business rules, process visibility, process flexibility, and AI are also available. Learn more about SAP Build Process Automation in our learning journey: Create processes and automations with sap build process automation

SAP Build Work Zone

Centralizes access to relevant business applications, processes, information, and communication in a unified entry point that users can access from any device. Administrators and users can benefit from a wide range of options to share and find all information rapidly and collaborate with each other, for example, blogs, multimedia, surveys, polls, wiki pages, events, knowledge base articles, tasks, and feeds. Learn more about SAP Build Work Zone in our learning journey: Implement and administer sap build work zone

Development Tools

The SAP Business Application Studio is the choice for the future from SAP. It's a modern, flexible, and extensible development environment for building applications for the intelligent, sustainable enterprise. It provides a common development environment for your professional developers and citizen developers independent of the devices and operating systems they are using without missing any tool for modern cloud development, especially specific tools required for business application development in the SAP ecosystem.

We have an own Learning Journey for SAP Business Application Studio with a lot more information you can find here: develop-full-stack-applications-using-productivity-tools-in-sap[1]business-application-studio

The ABAP Development Tools (ADT) is a collection of capabilities regarding ABAP programming based on the Eclipse IDE. It can be used for programming ABAP for on-premise purposes and for ABAP codings for the ABAP environment of the SAP BTP.

You can get the ADT from here.

For installing ADT, see this file.

The SAP BTP cockpit is the tool of choice for all administration or operational tasks.

Example of Development Frameworks from SAP

The ABAP RESTful Application Programming Model (RAP) is a framework for developing end-to-end, SAP HANA-optimized OData services, such as Fiori applications, in the ABAP environment. RAP supports creating various types of Fiori applications and publishing Web APIs. It uses technologies like Core Data Services (CDS) for defining detailed data models and a service model infrastructure for creating OData services compliant with the OData protocol. RAP also involves ABAP-based application services to implement custom logic and integrate with SAPUI5-based user interfaces.

RAP projects typically start with data modeling using CDS, where you define the data structures and relationships. Then, you specify the behavior of your data model, determining what operations can be performed, such as creating, reading, updating, and deleting data. This is followed by creating OData services that expose your data model and its capabilities through standardized protocols. These services can then be consumed by various front-end technologies, including SAP Fiori, SAP Build products, or third-party frameworks like React and Angular. Key components of RAP include:

• Core Data Services (CDS): A universal language for defining data models.
• Service Model Infrastructure: Tools for creating OData services.
• Behavior Definitions: Guidelines for how data models can be manipulated.
• ABAP-based Application Services: Custom logic implementation using ABAP.

Learn more about the ABAP RESTful Application Programming Model here.

IV. SAP BTP: Integration

APIs Overview

You encounter APIs in everyday life without you realizing it. An example is Google Search: Every time you enter something into the search bar, Google's back-end service looks up your keywords in its database and lists your request's results on the website. Actually, the website displays the API's result. An indicator for this is the URL of the respective search.

When thinking of a search for "SAP", the URL states: www.google.com/search?q=sap. Now let us slice this one down: Here www.google.com is the server address, /search indicates the feature you intend to use, or better, the API you want to call, which in this case is the Google Search API, and q (for query) tells it that now a value for query is handed over, which is the search term.

REST APIs as the most popular API type.

SAP Business Accelerator Hub

The SAP Business Accelerator Hub offers you a wide range of sandbox APIs for several SAP products like SAP S/4HANA, SAP BTP, SAP SucessFactors, SAP Concur, and more. You can use these sandbox APIs to create extensions, applications or integrations and test these with testing data provided through the sandbox API. All you need is the API key to authenticate your requests. You can get your API keys by logging in with a SAP ID account on the SAP Business Accelerator Hub and choosing Show API Key on the specific API page.

You can access the SAP Business Accelerator Hub here: https://api.sap.com/

SAP Integration Suite

SAP Integration Suite is an integration platform as a service (iPaaS), a service in SAP BTP you use to integrate business processes and applications. You can use prepacked, out-of-the-box integration, open connectors, or the holistic integration capabilities. You can also use AI-driven integration to simplify the development of integration scenarios.

SAP Integration Suite is the choice for all your integration scenarios.

See here: to get more information about the open connectors

Learn more about SAP Integration Suite in our free learning journey, Developing with SAP Integration Suite

V. SAP BTP: Data and Analytics

SAP Business AI

SAP AI Services

Automate business processes to enrich the customer experience by using SAP AI Business? Services.

SAP AI Launchpad

SAP AI Launchpad is a multitenant software as a service (SaaS) application in SAP Business Technology Platform. Customers and partners can use SAP AI Launchpad to manage AI use cases (scenarios) across multiple instances of AI runtimes (such as SAP AI Core).

SAP AI Core

SAP AI Core is a service in the SAP Business Technology Platform which is designed to handle the execution and operations of your AI assets.

SAP HANA Cloud

SAP HANA Cloud embeds several machine learning libraries, designed and optimized for massive parallel in-memory processing. There are two major components available within SAP HANA Cloud, which can be used for machine learning:

• PAL – Predictive Analysis Library
• APL – Automated Predictive Library

The Vector Engine in SAP HANA Cloud enhances Generative AI by using retrieval-augmented generation and embedding vectors for context. This could, as an example, aid a retailer in understanding customer buying patterns drawn from sales data. It refines large language models by obtaining current facts from an external knowledge base and offers insight into the generative processes. It also conducts vector searches and integrates these results with other SQL operations.

SAP Datasphere

SAP Datasphere serves as a central hub for gathering and processing data from various sources. By using AI, it not only simplifies sorting and analyzing this data, but also constantly learns to predict trends, for instance, foreseeing customer preferences based on their past behavior, saving substantial time and effort.

Learn more at: Artificial-Intelligence

VI. User and Authorization Management

Your company must manage application users (business users) and platform users (admins, operators, and so on). You want to assign roles and authorizations and build a central identity provisioning with the SAP Cloud Identity Services. All APIs and interfaces that are used or integrated need to get secured as well.

Platform users: are usually administrators or operators (DevOps) who work with cloud management tools and deploy, administer, and troubleshoot services on SAP BTP. These are usually users who directly log on to SAP BTP cockpit and work there. These also can be developers who work and use services in Cloud Foundry spaces.

Business users: use the business applications that are deployed on SAP BTP. For example, the end users of a deployed custom application or users of subscribed apps or services, such as SAP Business Application Studio, are business users.

The SAP BTP is organized in global accounts on the highest level. A global account is a reflection of a contract with SAP. It can consist of several directories and/or several subaccounts that provide different applications and services to users.

Subaccounts can have up to three environments: Cloud Foundry, Kyma or ABAP environment. The environments allows the development and administration of business applications with different approaches and tools based on your selection. Of course, inside of the environments and their content, such as the runtime, service instances and so on - there are also users required for providing access and authorizations.

When a customer signs a contract with SAP, one user is created at the global account level. On this level, entitlements are defined, assigning entities and services, including billing information. The global account administrator can initially log on to SAP BTP to manage these entitlements, and create directories and subaccounts. To ensure that more than one employee can administer the global account, the administrator needs to create other users at the global account level and assign them administrator permissions.

The subaccount administrator can manage entitlements, service subscription, create other users on the subaccount level, and assign roles to the users. Subaccount administrators get administration authorizations for the subaccount only, not for the global account.

Subaccount administrators also create business users. Business users are consumers of applications and services that are provided on SAP BTP (for example: SAP Business Application Studio) or business applications (SaaS) that were created with the help of the tools and services provided by SAP BTP. These users can have access to SAP BTP, but they are not able to do any administrative tasks.

Learn more about working with users in SAP BTP in the official documentation.

To use different functions of SAP BTP, you need to be authorized for it. You can configure authorizations using roles and role collections.

Role Collections

Role collections consist of individual roles that combine authorizations for resources and services on SAP BTP. A role collection can comprise of one or multiple roles. You only assign role collections to users, but not individual roles. Roles and their authorizations are provided automatically to users via role collection assignment. Role collections are managed on each SAP BTP level separately. Role collections that exist in the global account do not exist in the subaccounts. Likewise, role collections in subaccounts are not available in the global account.

To set up administrator access for platform users in the global account, directories, subaccounts, and so on, an existing administrator of a certain level on SAP BTP assigns predefined role collections to other platform users.

Roles

The roles are provided from the SAP BTP services you use and the developers delivering the role templates for the services. When enabled from the service, it is possible to customize these role templates. For a lot of scenarios, this is not possible and you need to go with the roles provided by the service, and can start composing them into role collections and assigning these role collections to users. It is also possible that the developers from a service provide role collection templates, but besides that, you can always create own role collections.

NOTE:

All users of SAP BTP are stored in identity providers. How you assign users to their authorizations depends on the type of trust configuration with the identity provider. If you're using the default trust configuration with SAP ID service, you assign users directly to role collections. However, if you're using a custom identity provider, you can assign role collections to individual users directly, or you map role collections to user groups or other user attributes defined in the identity provider. This is called federation.

Find more information in Assigning Role Collections.

SAP Cloud Identity Services

Applications and services in SAP BTP and even the SAP BTP cockpit do not store user information. Instead, a redirect for authentication to an Identity Provider (IdP) is required. This concept makes it possible to decouple and centralize authentication functionality from application capabilities and authorization management. The SAP BTP offers the possibility to use the SAP ID Service or custom Identity Providers from your IT landscape.

SAP ID

Service is the default identity provider in SAP BTP. It is a pre-configured, standard SAP public IdP (account.sap.com) that is shared by all customers. It has a pre-configured trust connection to all SAP BTP subaccounts. The SAP ID Service is fully managed and provided by SAP and you are only able to create a free user inside of this SAP ID Service. The SAP ID Service is also used for official SAP sites, including the SAP developer and partner community. It is the place where the S-Users, P-Users and D-Users are managed.

For many customers, users might be stored in corporate identity provider. SAP recommends using SAP Cloud Identity Services – Identity Authentication Service (IAS) as a hub.

The SAP Cloud Identity Services consists of two services: Identity Authentication and Identity Provisioning.

Identity Authentication service is mainly responsible for the authentication & single sign-on

• Provides simple and secure access to web based applications with a variety of authentication methods at anytime and from anywhere.
• The service has the task of validating the authentication between IdPs and the applications itself that is based on supporting open standards like SAML, SSO, and more.

Note:

SAML Security Assertion Markup Language (SAML) is an XML-based open security standard to exchange authentication and authorization data between parties like identity provider and service providers.

SSO Single sign-on (SSO) is a mechanism allowing the user to log on with a single user ID and password for several software systems. A full SSO enables the users to enter several systems, entering the credentials just once, for example, at the start-up of the computer.

Identity Provisioning service takes care of the identity lifecycle management, which includes both users and groups (things like create, change, delete, etc.).

Identity Provisioning service offers you:

• Manage user accounts and authorizations.
• User stores in the cloud and on-premise.
• Centralized end-to-end lifecycle management of corporate identities.
• Fast and efficient administration of user on-boarding.

Learn more about SAP Cloud Identity Services - Identity Authentication here.

SAP Authorization and Trust Management Service (XSUAA)

XSUAA is a component of SAP BTP that manages user access and permissions for applications and services, ensuring that only authorized individuals can access sensitive information and functions.

The XSUAA service, inside of the SAP BTP, handles the authorization flow between users, identity providers, and the applications or services. The XSUAA service is an internal development from SAP dedicated for the SAP BTP.

The XSUAA service does not store users data or user records. The XSUAA service needs a trusted connection to an identity provider. This can be the SAP ID Service or another corporate identity provider which was integrated to the SAP BTP. This can be made via SAP Cloud Identity Services - Identity Authentication Service (IAS).

The XSUAA service acts as the central infrastructure component of the Cloud Foundry environment at SAP BTP for business user authentication and authorization. SAP has enhanced the Cloud Foundry UAA by adding a service broker, multi-tenancy, management API functions, and some minor enhancements. XSUAA uses OAuth to authenticate between several services and connecting to the identity provider.

OAuth is an open standard for applications and websites to handle authorization. OAuth doesn’t share password data, but instead uses authorization tokens to prove an identity between consumers and service providers. It is an authentication protocol that allows you to approve one application interacting with another on your behalf without giving away your password. The tokens used from OAuth are called JWT tokens. JWT (pronounced “jot”) is an open standard that defines a compact and self-contained way for securely transmitting information between parties. JWT is widely used in OAuth for securely transmit user information and access rights.

Learn more about the Cloud Foundry UAA here.

Learn more about SAP's XSUAA service here, and here.

Learn more about OAuth here, and more about JWT Tokens here.

When a business application consists of several different apps (micro-services), the application router is used to provide a single-entry-point to the business application. Technically, an Application Router is a Node.js based app, available in the public NPM registry. An App Router got started based on a configuration file called xs-app.json. Inside of this file, it is defined which routes are served by this App Router and which XSUAA service instance is bounded to the App Router to handle the authentication requests.

An App Router is used to:

- Serve static content or files.

- Authenticate users.

- Dispatch request to back-end applications (micro-services).

In conclusion: The App Router is forwarding authentication requests to the XSUAA service, routing between the apps or micro-services, and if existing in the project, the App Router is also serving static resources like documents or images in a file system structure.

Learn more about the SAP App Router in the documentation.