Enterprise API - The only IT strategy that matters

nemanjko Sep 18, 2016 Architecture


We all know there is a problem with IT in today's enterprises. The CIO knows, the CFO knows, the CEO knows and everyone below them knows. Architects, Operations, Developers definitely know. The problem however still persists.

We would all love to have the perfectly connected IT systems behaving like clockwork. Systems that are maintainable, extendable, affordable, performable and many other XXXable’s.

Figure 1: How we wish IT systems would work together

Unfortunately, the reality of a typical IT landscape in a large enterprise is much more chaotic. Systems that are everything but the above XXXable’s.

Figure 2: How IT systems are interconnected in reality

The reason why the problem still persists in today’s enterprises is the complexity. Years and years of projects after projects that added new functionality on top of the old legacy.

Even though everyone accepts that there is a problem, nobody is willing to address it properly. It's a huge elephant in the room that everyone is ignoring. The reason is that there is no obvious solution to the problem. It's almost impossible to untangle all those dependencies. It's even impossible to document it properly, let alone to fix it.

Many enterprises just accept as-is situation. The IT systems they use are outdated but still good enough to do the work.

As Tom Goodwin stated in his article: We are at the peak of complexity – and it sucks. We live in a hybrid of old and new world systems. We use Slack and WhatsApp to communicate with other developers but then send status reports as emails. We use fancy mobile apps to book our flights but then we do the check-in at the airport where the staff is still looking at screens with green desktop applications.

Legacy IT systems are built to last. It's more probable that an enterprise itself will cease to exist before their IT systems stop working. Even if an enterprise survives the competition and the market pressure, their problems won't be the IT systems themselves, but the people who have the knowledge to maintain those systems. Try to find a Cobol developer these days who is not retired. If your key systems are written in Cobol, you already have an issue.

The solution is not an IT strategy that will decommission a few of big systems just to be replaced by newer ones. Dependencies still stay. The problem still exists, just is postponed to another era.

The real solution in tackling complexity has been known and used by programmers for a very long time. That solution is known as the Facade Pattern. The Facade Pattern hides the complexities of the system and provides an interface to a client. The client can access the system using the facade. The role of the Facade Pattern is to provide different high-level views of subsystems whose details are hidden from users. Hiding detail is a key programming concept. What makes the Facade Pattern different from other patterns is that the interface it builds up can be entirely new. It is not coupled to existing requirements, nor must it conform to existing interfaces.

Facade Pattern thinking can be applied to whole enterprises as well, not just a low level code. API Services are an example of a Facade Pattern. The only IT strategy that could reduce complexity produced over many years of development & merging & acquisitions is to hide all that complexity and start thinking about API services that your enterprise has and cares about.

The “API” stands for “Application Programming Interface”. The name itself has roots in the 1970s when the C programming language was just picking up. The name alludes to externalization of low-level application interfaces. The name API works fine on the application level where different components need to be loosely coupled and separated by interfaces. On a higher level however, the name API is a bit misleading. When we are talking about enterprise API management, we do not care about internal application API’s. We care about functions that are useful to a user/client/customer.

As an example, a typical enterprise system is a document management system. Document management systems have hundreds of internal API’s, but as a user we basically need only two functions – GetDocument and PutDocument.

Another example might be Human Resource system that is managing records of all internal employees of a company. Such systems have hundreds of functions. But from the outside, we can start by externalizing only few that can be useful to some employee portal – FindEmployee, AddEmloyee, RemoveEmployee.

When we start thinking in this direction, our complexity suddenly becomes more manageable.

Figure 3: Exposing Enterprise API's

New projects should not be another brick in the complexity wall anymore. They should be just temporary views into our existing enterprise API services. Applications will come and go as they should, but the enterprise API services need to stay.

A new customer portal should only use enterprise API’s that are exposed. It should not be concerned with the legacy complexity. Internal complexity needs to be managed by a set of aggregated services that are orchestrating access to all the internal systems that are needed to fulfill the high level API call.

Figure 4: New Customer Portal using Enterprise API's

Over time, internal systems can be replaced/decommissioned without impacting newly built applications that are using their services. Enterprise operations continue to work without interruption while the whole technical debt is being paid in gradually.

With this architecture in place, when we need to upgrade one of the existing applications to a new version, or replace the entire application with a new one, the existing HR Services, Document Management Services and Policy Management Services layers protect our API consumers from being affected by this change. It is in those layers that we can reliably define reusable business rules and convert between logical interfaces for the new Customer Portal Application and the application specific interfaces of our back-office applications. 
So what happens when we publish only logical, application neutral services through our API Management layer? It turns out that we will naturally be publishing APIs that make sense to our enterprise. We will be building an interface to our enterprise. We will be doing all of our customers a favor by doing so, since it has a greater chance of setting them on the right path from the very beginning.

API management can be taken even a few steps further. Enterprises can implement three levels of API management:

  • 1. Client API Management – entry point to all front-end services used by client applications
  • 2. Enterprise API Management – entry point to all backend services used by front-end services
  • 3. Data API Management – entry point to all data sources used by backend services

Implementing Enterprise API strategy is never a technical issue. Many modern software products are already exposing most of their functionality via API’s. They are usually built with microservice architecture where API’s are in the heart of the solution. They are the contract between each microservice. Older monoliths are not there but still there are ways to “interact” with them – e.g. building a layer around the monolith that exposes REST API endpoints but internally is mapping them to native calls to the business components (see StranglerApplication pattern).

The problem with Enterprise API strategy is the same as with any other IT strategy. It requires buy-in and support from the highest levels in the company.

In 2002, Jeff Bezos (Amazon CEO) sent an email to all employees where he mandated usage of API services:

  • 1. All teams will henceforth expose their data and functionality through service interfaces.
  • 2. Teams must communicate with each other through these interfaces.
  • 3. There will be no other form of inter-process communication allowed: no direct linking, no direct reads of another team’s data store, no shared-memory model, no back-doors whatsoever. The only communication allowed is via service interface calls over the network.
  • 4. It doesn’t matter what technology they use.
  • 5. All service interfaces, without exception, must be designed from the ground up to be externalizable. That is to say, the team must plan and design to be able to expose the interface to developers in the outside world. No exceptions.
  • 6. Anyone who doesn’t do this will be fired.

As the outcome of this, the leading cloud provider Amazon Web Services (AWS) was born where every service in AWS is API driven.

API management requires ownership. It requires dedicated API Management Office with API evangelists who can teach development teams how to externalize their functions as API’s. It requires setting up new governance processes, rules, standards and guidelines to monitor the implementation of the enterprise API strategy.

There are many of API management tools on the market. The common name that emerged recently for them is API Gateway.

API Gateway services have a multitude of features. Their main focus is to make designing, deploying and managing an API easier, as well as to ensure that it is safe, secure and functional.

Some of the benefits of using API Gateway solutions are:

  • 1. Documentation – one of the most common problems of developers is figuring out how an API works. An API management service has to provide an easy way to read the documentation and enable developers to “try before they buy”.
  • 2. Analytics and Statistics – it is critical to understand how people use our API and get insights for our business.
  • 3. Deployment – should be flexible and support public or private clouds, on-premises implementations, or combinations.
  • 4. Developer engagement – engaging with API consumers, developer or partners is important. Getting an easily accessible developer portal will significantly facilitate on-boarding.
  • 5. Security – API’s carry sensitive data, so it is important to protect the exposed information. The service has to at least provide identity and access management for users and developers.
  • 8. Availability – should be available, scalable and redundant. An API environment can become demanding and the service should be able to deal with any kind of errors, problems or temporary traffic spikes.

Popular tools on the market for API management are:



To be flexible, cost effective and to adopt rapidly to changing customer expectations and behavior, all enterprises should consider and adopt an Enterprise API Strategy. An enterprise being able to answer “what are my key Enterprise APIs?” might be the difference between failing and succeeding in the millennial and post millennial era.



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