Building bridges is hard

In a world where everybody builds distributed system (in a small scale: for microservice-based systems; in a larger scale for a global market) and time to market is a key success factor, we face the challenges of parallel development and synchronization across teams and products. While agile frameworks like SCRUM address some of the arising topics (e.g. having a unifying definition of done for multiple teams) there are other means to tackle the complexity.
But before we jump to a solution, let’s take one step back and review one of the typical issues:

  • One team or company builds an awesome API and another team integrates it into their product.
  • The second team must wait for team one to have a working API before they can start their integration work. However, even after they waited for team one to finish, they face mayor problems during their development.

These could occur while working with the API directly but might as well be totally unrelated (e.g. when trying to automate an unclear business process). The reasons don’t matter that much when the second team’s product arrives the market too late and lost its worth.
We (i.e. software engineers) solved these kinds of problems on other layers already. When building a database-heavy application we start with the data model (+ database) and then build the user-facing application and the data-oriented pipelines, optimizations etc. in parallel – instead of sequential development. We call this database first.


So, let’s talk about API first…

The idea is not complicated: two (or more) teams design an interface collaboratively. Usually, this is achieved by a proposal from one team and following discussions. The result should be an interface description that all parties agree on. In our case we are going to use the OpenAPI specification (or swagger if you don’t look too closely). We can create an example for our case here: here or here.
Disclaimer: There a lot of pay-versions out there, but these two are free and without registration. So, they are either nice or steal your data.

For the example in this post we want to create an API used for a room-booking service (think about it like the outlook room booking feature for meetings). We’ll start with two endpoints

  • GET /rooms gives a list of all available rooms and
  • GET /roomdetails provides more specific information for a given room

For good measure we throw in a technical service endpoint with

  • GET /health that provides a simple ‘ok’ in case our service is up and running.

Using one of the API designers and only minimal features of OpenAPI we end up with our swagger.yml:

swagger: "2.0"
  description: 'a simple room booking service'
  version: 1.0.0
  title: room booking service

basePath: /v1

  - http
  - application/json
  - application/json

      operationId: ''
          description: 'get service health'
      operationId: ''
          description: 'get all rooms + meta data'
      operationId: ''
          description: 'get details for a room'

Before we implement our (mock) API, we create our webservice with these six lines of code (

import connexion

app = connexion.App(__name__,
                    options={"swagger_ui": True})
application =

if __name__ == '__main__':, server='gevent')

Before we explore what we see here, we’ll install our dependencies first. There are multiple ways to do this in python, but for the easy way we use pip and our requirements.txt. For people unfamiliar with python, this would be like npm & package.json for Nodejs or maven & the pom.xml in Java.


Connexton is an API-first framework build in python by Zalando (Open Source). It leverages popular technology components like Flask and Oauth2 and integrates various industry standards to fasten up (microservice) development.

Gevent is a python networking library that is used as a WSGI server in this case. For our purpose we do not need more information on this, but if you want to dig deeper, check out this excellent blogpost.

Now, let’s come back to our code! As you can see, we create a new connextion.App(...) with enabled swagger ui and add an API (reference) the app exposes (our previously created swagger.yaml). We are pretty close to running our API-first application.

Connecting the dots

For the last steps, we need a mock implementation of your endpoints. In a real-world example, you should have defined responses in you swagger specification already. A variety of tools can generate server mocks from this. However, as we have a slim example, we create this without any tooling help.
Considering our current project structure, we’ll just add two files for our API-controllers. We create an api/ folder with two subfolders for our "business" logic and our technical health-endpoint ( and
|-- business_controller
|   `
|-- tech_controller

Simple mock-returns for and

def get_room():
    return ["Kallista", "Io"]

def get_room_details():
    return [{"name": "Kallista", "space": 3},{"name": "Io", "space": 4}]
def get():
    return 'ok'

Ok, let’s review what we got so far…

  • We have an API specification (at this point another team could start their work).
  • We created a lean python webserver that exposes our API from our specification.
  • Lastly, to actually run this, we coded a trivial stub implementation of our API.

The last thing we need to do is to connect our API routes to our controller functions. This is easily done by enhancing our swagger.yaml slightly (adding the path to our controllers as operationId):

swagger: "2.0"

  description: 'a simple room booking service'
  version: 1.0.0
  title: room ms

basePath: /v1

  - http
  - application/json
  - application/json

          description: 'get service health'
      operationId: api.business_controller.rooms.get_room
          description: 'get all rooms + meta data'
      operationId: api.business_controller.rooms.get_room_details
          description: 'get detail for a room'

Explore and verify our API first mock service

Now let’s enjoy our service:

~/DEV/wellroom-room$ pip3 install -r requirements.txt
~/DEV/wellroom-room$ python3

We could call our API now at http://localhost:3000/v1/health or http://localhost:3000/v1/rooms with a tool like Postman or Insomnia, but we can also serve to http://localhost:3000/v1/ui/ and explore the API via the build-in swagger-ui function in a browser.

Wrap up and what we didn’t cover

We learned about the benefits of API first and saw one way to approach the topic. We got a short glimpse at what python with connexion can do for us. From tooling standpoint, we saw tools to create OpenAPI specifications.
The two main things we are missing at this point is the security component and quality assurance (e.g. testing + linting). The first part is a topic on its own, but one of the great benefits of using connexion is the native integration of standard mechanisms like Oauth2 and X-API-KEYs. For testing and linting there are great blogs, books and videos out there….😉

Follow up

This blogpost is part of a series.

  • The next post is going to focus on how to integrate such a microservice in an enterprise ecosystem:

    • Dockerize the application,
    • use Azure Container Registry to store our application,
    • create and access an Azure Kubernetes Service and finally
    • deploy our service in this Kubernetes cluster.
  • The third post shows how to enforce improvement with continuous delivery and/or continuous deployment for our room service:

    • leverage AzureDevOp’s Build and Release Pipelines for our service and
    • integrate our Kubernetes cluster as environments in AzureDevOps.

In data analytics, there are a lot of nice and shiny buzzwords, products and concepts. Before you decide anything, you should be clear about your actual and future needs. Your analytics infrastructure should enable you to analyze data. But there are aspects that architectures support differently and you have to trade off. There is no free lunch.

Here are some explanations that should help you to orientate what you need and enable you to compare different approaches.

Data Location

It’s important where the data is located. You can leave the data on the source system and read it per analysis. Or you can copy the data to an analytics system.

Pros of leave and read are:

  • You will save space.
  • You will have always the most recent data.

Pros of copy are:

  • You may get fast analyses, since you can optimize the storage for analytics.
  • You maintain fast operations, since you don’t read data that the source system wants to use at the same time.
  • You get consistent results, since you control the updates.
  • You can implement historization and don’t lose information.

Usually the data is copied, but if the volume is big enough or you don’t have the resources you may want to leave it on the source.

Data Structure

How or if your data is structured has a significant impact on your analytics infrastructure. There are structured data, semi structured data and unstructured data. Structured data are for example relational databases. Semi structured data contains information how to separate values and identify structure. Examples for tabular semi structured data are simple Excel sheets or CSV files. Examples for hierarchical are XML or JSON that are often used by web services and APIs. Examples for unstructured data are images, PDF or plain text.

Analytics is all about reduction of information to be consumable by humans or processes that humans create and understand. Reduction requires structured data. Semi structured data can be transformed into structured data. Unstructured data may be transformable into structured data, but not always, not that easy or not error free. Avoid Excel, PDF or Text as data source, whenever possible.

Data Transformation

Data from different sources may be hard to combine, since there is no common identifier or different formats. There are again two approaches: "Schema on read" and "Schema on write". "Schema on read" means, you leave the data in its raw form and transform it when you analyze it. "Schema on write" means, if you write the data you transform it into a common format. You may change the format, the data types, normalize it and deduplicate it.

Pros of "Schema on read" are:

  • You may save effort on integrating new data.
  • The raw data may contain more information than the integrated data.

Pros of "Schema on write" are:

  • It’s less effort for analyses using integrated data in development and computation terms.
  • Investment in quality pays out more, due to the reuse of transformed data.
  • Preaggregated data will speed up analyses.

Data Volume

It’s hard to say what data volume is big, but anyway it should have a big influence on your individual solution. In analytics systems, performance is often provided by redundancy. Some results that are used several times or with reduced latency are precalculated and stored.
So one piece of information is stored many times in different ways. That’s performance efficient but not storage efficient.
Obviously that may be a problem with a lot of data.

Usually one can say that data that is automatically generated, e.g. from sensors or logging functions may come in high volumes. Manually generated data like orders in your ERP system or master data usually not.

Data Velocity

Data velocity means how much time elapses from data generation to analysis. High velocity may come along with other restrictions or increased effort.

Most common are scenarios with updates on a daily-basis. For regulatory supervision it may be enough to update your data once a quarter.

A often misused term in this topic is real-time. If your system is real-time capable, it means that you guarantee a result in a specified time. That’s important for example in embedded systems in automotive or industrial environments. In business context real-time is used as best effort latency and only in special cases necessary. Imagine a manager that makes decisions, based on reports that are updated and changed every 5 minutes. That holds the risk to react to random events instead of pursuit a strategy. That may be different in a cloud-based application scenario, where you want to scale-up or scale-down the system based on the usage. Or think about a process that changes the prices in a ecommerce scenario based on the recent sales.


You see if someone tries to sell you something without listening to your requirements, there is a good chance to end up with something that does not deliver what you need or may be accomplished with less effort.

As IT consultants, we try to solve problems on a daily basis. This is our normal workload, our daily business. But this is not our only duty, we need to keep up with the technical evolution, we need to learn continuously to satisfy our customers. This is why we read about new things in blogs, visit meetups in our free time and go to conferences (like the one this post is inspired by "down to earth architecture" by Uwe Friedrichsen @SAS 2019 in Munich). We are influenced by all these channels and need to be careful how to use the knowledge in our working environments or we end up with one of these stereotypical types of bad software architecture:

Stackoverflow architecture (or google-driven architecture)

We have a problem to overcome in our software system and are not familiar with the topic. Therefore, we search the internet for books, blogs or tutorials. We find a slightly related solved problem on Stackoverflow and copy the solution without much thinking.
We are not talking about copy-pasting code here, but rather abstract solutions like "where should ids be generated in CQRS." We do not want to downplay the absolute knowledge found on Stackoverflow, but we should be sure the solution we found actually fits the problem and/or adapt accordingly.

Conference-driven architecture

Whatever conferences you visit, you always feel attached to your track or topic. These could be things like micro-services, domain-driven design or EventSourcing. While these are very good solutions to their respective problems, they might solve problems you aren’t even encountering in your domain or there are other good solutions.
Additionally, most of the time, we are not starting an application from scratch. If we visit conferences regularly and always incorporate the hot topics, we end up with a mess after some time.

Hype-driven architecture

Similar to the conference-driven architecture, we find the hype-driven architecture. Every (new) application needs to be distributed into micro services. Of course, that’s not true. There are huge benefits in following a micro-service (or SCS) approach, but there are also challenges, constrains and problems! Learning and especially applying a framework is often useful. However, you should not force a framework onto your system if there is no need for it! Most of the time, learning how to solve your domain’s problems (e.g. how to handle consistency in distributed systems or mastering personal data and GDPR) is more beneficial than being a master of a framework.

Strategic architecture (aka PowerPoint architecture)

Usually, when you join a project there are some PowerPoint slides describing the architecture of the system or application. You go through these, but your colleagues advise against doing so: "these are for compliance" or "we made this for the latest steering committee". When the slides diverge too much from the actual structure or code, misunderstandings are about to happen! While there are reasons to display different aspects of your software to different stakeholders, try to minimize this.

Tunnel-vision architecture

As a software engineer or architect, you need to work on some topics in excessive detail. We need to build walls around us and analyze problems in-depth! Occasionally, we need to look around, too. With more experience, we learn to balance the extremes. Especially for younger developers, there is a risk of over-engineering one detail or creating problems on other ends of the system.

Blast-from-the-past architecture

Technology advances, business models evolve and the underlying software architecture needs to do this, too. There are challenges that a lot of software components face; an example is versioning of web APIs. A versioning concept of system-to-system APIs with /v1/, /v2/, /v3/ might work for applications that had a release once a month and a breaking change once a year, but probably won’t work for a fast paced API in an API economy where time-to-marked is a driving factor.

Big design up front

In a world with perfect information, where all user needs and every aspect of your system are clear, Big Design Up Front (BDUF) could work. BDUF is closely related to the waterfall approach of developing software. This clashes with the agile world. Similar to communism and capitalism, BDUF and agile development are two paradigms where neither is inherently bad or good – it’s just that one is more practical in real life. Especially in a fast-moving world where innovation is key, agile development won the battle and there is no place for BDUF architecture.

One-size-fits-it-all architecture

Develop your application as a polyglot, domain-driven micro-service architecture with CQRS and EventSourcing. Use Kubernetes as container orchestrator with Helm for deployment, Prometheus and Grafana for monitoring and GIT as source control system. Frontend is Angular, machine learning is done in python and we use Mongo and Cassandra for persistency. Caching is done through redis and the whole application needs to be cloud agnostic and conform to all cloud native principles. While this is a noble approach and a turn-on for software engineers, this might not suite our business needs in any way. We could solve many problems with this technology selection, but we are likely over-engineering and not optimizing our efforts.

Accidental architecture

Remember the cone of uncertainty? When you start developing a product, about everything is blurry. You don’t know the user-needs; you don’t know the scale of your application and so on. At this stage, you might not be able to find solutions to some problems as you cannot answer essential questions. At this point, you need to act accordingly! Work with interfaces, adapters and libraries that can be switched later easily or don’t put too much effort in some components as you will either replace them later or implement a more sophisticated version anyways.
Don’t just "do it" or you will end up with a mess of decisions that nobody wanted to make. Another way accidental architecture happens is the development team is either unaware of or under-experienced to identify key-issues.

How do we make sure not to end up with one of this? I’ll look for a more detailed answer in another article, but it boils down to this: we should ask why we need architecture initially.
We have requirements, constrains, problems etc. We figure out solutions (for example with an approach like "orient – explore – evaluate – support" from Uwe Friedrichsen). When we follow this path, we protect our systems from the types of bad architecture above. As unlikely as it seems, if we end up with an architecture that is similar to the ones above, it’s fine. We engineered it with the right intentions. Additionally, learn when to not use certain solutions and follow Uwe Friedrichsen’s advices:

  • Think holistically
  • Resist hyper-specialization
  • Get a T-shape profile
  • Leave your comfort zone once in a while
  • Understand your domain
  • Don’t fall for hypes
  • Cope with technology explosion
  • Master the foundation design
  • Don’t overact

Software development is hard. Sure, there are things that can make your live easier (e.g. Containers or ubiquitous language), but sadly there is "No Silver Bullet" as Frederick P. Brooks Jr. concludes in this 16-pager. With our advance in technology, development becomes easier and faster. But some things may not bring the redemption we hoped they were (like "automatic" programming code or even OOP and somewhat newer AI).
One of the more promising members of the redemption-club is the "Great Designer" (p.15) of the software system. They build software "faster, smaller, simpler, cleaner […] with less effort". Today, we call someone with the skillset described by Brooks a "software architect".

In 2019, I went to a great Summit in Munich where Trisha Gee (@trisha_gee) held the key note about required skillset for a software architect. I want to share her insights mixed with my views here:

Master of communication

The software architect is a master of communication. Obviously, this is not limited to verbal communication, but also includes writing skills. Writing does not stop with good programming and documentation skills. Things that matter are e-mails, slack and twitter! Asking questions like "what are we building?" and "what skills does the team have?" are as important as listening to the answers and translating it into software.

"Your code does not speak to the machine. It speaks to the next one who reads it!"

Talk to different people. Talk to developers, domain experts and users. Try to get a feel for their problems, challenges and constrains within their domain.

Adaptability & open minded-ness

Be openminded! There are a thousand views on a simple topic. Users und domain experts might change their minds rapidly, technology and processes change. It is your job to order things, estimate the impact and derive actions.

It’s not the year of K8s!

No, Kubernetes, AI and agile development are not the magic solution to every problem. Always learn what’s needed.

Prioritization & time management

We all work in projects. There is always too much work for too few people – deal with it. Allocate time for yourself. Make a plan for your work, for time at home and absolutely free time. Mental health is an essential part of a "Great Designer". As an architect, your time is limited and valuable. You cannot learn everything, but try to keep up.

Stay technical

Most of the things up until this point are non-technical. But be careful; do not underestimate the "Business Analyst Movement". Trisha points out that especially women are pushed into non-technical and softer roles too often. Don’t become a PM, stay an architect.

Scale out

At some point in the history of software engineering we got to the point where we understood, scaling out may be better than scaling up [Admiral Grace Hopper]. The same applies for great engineers. Instead of just getting better, help others to get better.

If you want to be 10 times more productive, teach 9 people your skillset.

Use "pair programming" more often, but do not stop at development. Do it for deployments and troubleshooting with a DevOps engineer and for domain building with a business analyst. Code reviews and walkthroughs "are not for finding bugs only – they are about sharing information and writing the best system you can". If your company supports it, Trisha recommends 20% time. Another idea to share are book clubs where five people read a book – one or two chapters each and tell the others about key information in their part. This way everybody can get a little knowledge and decide if it’s worth reading the whole thing.

"Nobody knows how good you are! Teaching makes you look good."

There are different ways of teaching and being taught. You can teach in internal, informal (or less formal) sessions during lunch time called

Visit user groups and speak on conferences. As usual, there are pros and cons for each type. Decide what’s the best for you.

If you don’t like sharing with foreigners, share with your colleagues. This way you avoid too narrow specialization and knowledge-silos.

Retention and recruitment

Being a good architect means finding new projects and interesting topics in your environment. That is the easy part. Also, watch out for new colleagues and keep your team(s) happy! Be a good role model, be a paragon for great designers.

Community support

We love stack overflow! We visit conferences and we gather at meetups. You cannot explore every technology yourself – especially not as an emerging architect. You need to consume what the community can provide, but you also need to give back. You can talk about your personal challenges when your first big project failed or you commit to an open source project: maybe there are easy enhancements for your favorite JavaScript library or you build a python wrapper for a public REST API.
Do you like Goldman Sachs? Probably. But aren’t they an evil banking company? Probably. Nevertheless, their developers are vivid contributors to Java libraries. They published their enhanced version of JavaCollections (called GS Collections) and influenced a lot of things like the Java Streaming API.
The same things goes for Microsoft. They open source their .NET Core platform as part of the .NET foundation and publish their code to the best IDE ever created on GitHub.