Health Interoperability
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The Buy or Build Question: Making the Right Choice For Your FHIR API

Rien Wertheim

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Are you deciding on your FHIR API too? You’re not alone. Not long ago we published a whitepaper called The Buy-vs-Build Guide to FHIR APIs. We wrote the whitepaper because we noticed that more and more decision makers and Software Architects in our network were asking the same question. Oftentimes they find themselves needing to implement FHIR for one reason or the other (a government regulation like the 21st Century Cures Act in the US, a top-down decision, or simply needing to improve an existing health IT system). Then the classic dilemma begins: do we build these FHIR capabilities ourselves or should we just buy them from a FHIR vendor?

FHIR’s journey from pilot project to a business-critical application

Since we published the whitepaper, it has become one of our most popular resources. The guide is downloaded daily all over the world, mostly in the USA. The demand for this decision-making tool exceeded our expectations. What can explain its popularity? We believe it’s proof that FHIR has entered a new phase of its maturity. No longer are we in the stage of pilot projects, proof of concepts or R&D. Implementers are now starting to build business-critical applications. Substantial and long-term investments are required and decision makers are asking their staff to prepare business cases before starting the development process. This is where the buy-versus-build analysis comes in. 

What is a FHIR API anyway?

In the guide a FHIR API is broadly defined as a back-end implementation of the FHIR specification, the RESTful API and data model published by HL7. More specifically, the FHIR API is on the server side of the equation. This can be a full server that stores FHIR data in a database, or a FHIR facade sitting on top of an existing proprietary database with some sort of translation layer in between. The definition of FHIR APIs does not extend to client apps. The guide does not apply to client use cases. 

FHIR API build image

What does it mean to ‘buy’ or ‘build’ a FHIR API?

The ‘buy’ or ‘build’ question isn’t so black and white. There’s a nuance. The extreme ‘build’ scenario is where you build a FHIR server from scratch, without leveraging any third-party libraries. Hardly anyone would go down that path, except, obviously, server builders and some large EMR vendors. Your typical health IT implementer would probably take one of the main open-source libraries (like HAPI FHIR for Java or the Firely .NET SDK for Microsoft .NET) and use these to build their FHIR server. This is how we define building a FHIR API. On the other hand, ‘to buy’ means purchasing a solution from one of the FHIR vendors like Smile CDR (HAPI FHIR) and the Firely Server (powered by the Firely .NET SDK). These solutions include support and maintenance. Buying a FHIR API can also mean subscribing to a managed service, like Google Cloud Healthcare API, Microsoft’s Azure API for FHIR, or AWS FHIR Works. These are what we place on the buy side of the equation.  

FHIR API buy or build guide preview
Download your own copy of The Buy-vs-Build Guide to FHIR APIs

Eleven things to consider when buying or building a FHIR API

The Buy-versus-Build Guide to FHIR APIs lists eleven parameters, dials if you will, that define the outcome of the analysis: 

  1. Control 
  1. Expertise 
  1. Bandwidth 
  1. Affinity 
  1. Timelines 
  1. Competitive Edge 
  1. Customization 
  1. Feature-completeness 
  1. Security 
  1. Compliance 
  1. Costs 

Each of these parameters are fully explained in the guide which you can download here. For instance, ‘Expertise’ refers to the level of FHIR expertise in your team or organization. ‘Timelines’ refers to deadlines you have to meet. Spoiler: the tighter the deadline, the more you will be inclined to buy.

FHIR API buy or build calculator
Preview of the FHIR API Buy-versus-Build Calculator

An Excel calculator for analyzing your use case

The Buy-vs-Build Guide to FHIR APIs comes hand in hand with an Excel calculator that contains all eleven of the items above. For each dial you can define the relevance from not important to very important, and the score that you want to apply to the parameter. For instance, for ‘Customization’ you can decide between “We require customization beyond the FHIR specification” or “The FHIR specification is sufficient for our use case”. Upon setting the weight and score for all the parameters, the Excel tool reports the outcome of the analysis with a result ranging from Definitely Build to Definitely Buy.

ISiK edition for Germany  

The original version of the The Buy-versus-Build Guide to FHIR APIs was created for the 21st Century Cures Act in the US. However, the contents of the guide and calculator are not restricted to this rule or even to the US jurisdiction. The setup is generic, hence the downloads from all over the world. Recently, we released a second edition for the German market for ISiK (Informationstechnische Systeme in Krankenhäusern). 

How to download the guides

The guide and the calculator are available as free downloads on the Firely website:

For questions or more information about FHIR APIs, the Firely Server, or a ready-made ISiK solution, send us an email at

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