A Successful Open Source Story Uwe Trottmann – SeriesGuide

A Successful Open Source Story Uwe Trottmann – SeriesGuide

We had the opportunity to interview Uwe Trottmann, creator and principal contributor of the app SeriesGuide with over 1 Million downloads on Google Play. 

Uwe Trottmann

Uwe Trottmann

Small Business Owner at SeriesGuide

He received his M.Sc. Computer Science at TU Munich in 2013 and is interested in making software usable for everyone. If at all, he is only looking for part time work next to his other endeavors.

Download SeriesGuide!

Dorian: For how long have you been coding?

Uwe: That’s a very good question. I started in school in 2004 because a friend of mine coded a basic vocabulary training program in Visual Basic. I started to improve that program and later enrolled in a programming class in school, which was very new at the time. Right now it’s common to have computer science classes in school, but back then it was not the standard. I started doing other side projects for fun, but only got serious about coding when I started studying computer science at University in 2008.

Dorian: Do you think going to University helped your projects?

Uwe: Yes, absolutely. There’s a lot of technical and theoretical background that you are not exposed to, if you just program. At University, the coding exercises were very easy for me, because I had a lot of practice beforehand. However, I learned so much about other things like designing systems, Software Engineering, how to manage projects. Also the theoretical background, like data structures, how to do things efficiently. Also things I never would have looked at, like computer architecture, how stuff works on the lower levels, etc. Which is interesting to know, but it doesn’t really help with the stuff I am currently working on. 

Dorian: But that knowledge of the lower levels has maybe helped you solve some bugs?

Uwe: It has a little bit. I think the only relevant thing that I still come across now is bit operations. But things like registers, or programming in assembler, no. This is probably more helpful for the C guys, which program at a lower level. I like working at a higher level. So I program in Java, Kotlin, for Android, and Windows back in the day. These all abstract the lower level away and I didn’t have to worry about memory management, which I didn’t really like doing back then. It’s complicated and very easy to get wrong. I don’t know if you have heard about pointers, but they are one of the biggest problems with programming in C. If you get a pointer wrong everything breaks, you have security issues, and so on. If you talk to C developers about pointers, they could go on forever.

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Uwe Trottmann at Droidcon Berlin 2018.

Dorian:  How did you start up with Open Source? Did you start right away out of University or did you do work for other companies and do Open Source on the side?

Uwe: In the beginning I had my own projects and didn’t know about Open Source. The first thing that I open sourced was SeriesGuide. My work on SeriesGuide started as a hobby because I had recently switched to Android and was missing the series management app I previously used on another platform. I first posted SeriesGuide to Google Code and then the Google Play Store in 2010. I later moved it to GitHub 2011. My work got more serious during my computer science studies at University. Once I started using GitHub, I added more libraries that SeriesGuide uses and I contributed to other projects on there as well. GitHub really accelerated the SeriesGuide development.

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SeriesGuide Statistics Screen

Dorian: Did having access to other Open Source projects help you develop SeriesGuide?

Uwe: Of course, it tremendously helped. I guess SeriesGuide is probably 80% other libraries, it’s Open Source so you can go check. Some of the API integration with the TV show database I used back in the day was an Open Source library, so I built on top of that. I then replaced it with my own later. Also if you know Jake Wharton, the Keynote speaker for Droidcon Berlin this year, he was one of the early contributors to SeriesGuide and I used some of his libraries in the beginning like ActionBarSherlock. Then later the networking and logging libraries he was working on. Obviously I used the Android Open Source libraries once they came along. SeriesGuide would not exist without Open Source software.

Dorian: Why did you choose Open Source as the foundation for your paid app?

Uwe: It started as free and Open Source at the beginning on the Google Play Store, because I was just a computer science student and didn’t have the need to make money. It was also rather complicated to charge money, because you have to set up your own company. Around three years after I posted it to the Play Store, due to people suggesting that I charge money, I started developing extra paid features, such as notifications, theming, and then later the syncing component.

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Shows on SeriesGuide

Dorian: Is the core of your project still Open Source and will it stay like this forever?

Uwe: The whole app besides the small server component is public domain. And the spec for the server component is open, so you could build your own if you wanted to.

Dorian: What is the best thing about SeriesGuide?

Uwe: Honestly, I’d have to say the community. Back in the day I had a few people who really pushed me to improve the app, like Jake Wharton, Craig, Chris, and other friends. They really helped me get SeriesGuide off the ground. Without them I would have fixed a bug or two, and then would have moved on. Because of the continuous requests and a growing community, I had to keep going and make it better. And without the community paying for the app, I wouldn’t have the means necessary to continue working on it.

Dorian: What do you dislike about Open Source?

Uwe: Honestly, in the beginning I thought open sourcing would be risky because someone could copy my app, slightly modify it and then publish it, taking credit for my hard work. Because of that I have a separate private repository with new features that I hold off publishing for a few days. But if I remember correctly, this only happened once and was not an issue because the developer didn’t continue development. I am not 100% certain it was a copy, but the code looked very similar to mine. Right now, I don’t think this is an issue anymore. If people use my app they expect my updates because I maintain the app. If somebody copies it, they don’t have my work power and knowledge.

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Uwe’s contribution to SeriesGuide on GitHub as of July 6th, 2018.

Dorian: How do you manage your time between developing Open Source projects and your work?

Uwe: I work Mondays and Tuesdays on my main job, kind of as a backup. The rest of the week whenever I have time, I work on SeriesGuide and related Open Source projects. Of course it never ends up being three days. If somebody wants to contribute, I welcome pull requests. I also allow people to translate the app into their language. If somebody has a bug to report, the easiest way to do that is on the website. If people want to contribute code, they can go to the GitHub contribute file which lists everything you need to know.

Dorian: Do you have more features in mind right now?

Uwe: There’s a feedback site where people can request changes, and there’s no shortage of suggestions! I also have ideas in mind, but some things are bigger and I don’t want to do them right away. It’s a constant struggle to get things done. I am not out of ideas; it’s more of a time problem right now.

Dorian: You have a very good time structure, which is encouraging. How hard is it to turn an Open Source project into a profitable business? How did the community react that you have built a business with paid features on top of an Open Source project?

Uwe: The overall reaction was positive. Obviously there are some people that aren’t happy with the presence of paid features. I always tell them that the app has no ads in the free version and you can do pretty much everything except for some convenience features. I would say that for most people this is not an issue because the basic functionality of the app is still freely available. One of the early complaints was that I charge too much money. So in the beginning I was charging 1€ as a one time payment for all access, then increased prices to 3€ per year or a 7€ one time payment. I explained this was to support myself and future updates, basically development time, and most people understood that. I clearly mention that inside the app, paying is not only to get some features but also to support me and future updates. So far most people like the idea and buy into it. Obviously, if you look at the share of paid vs free users it’s nowhere near something like 50/50, it’s way less. But I have a core set of users who believe in the app and support it financially. So far this method has gone well. I am also pushing people towards subscriptions now to secure future development.

Google play store java embedded database java object database livedata android Mobile Database open source database software qsl alternative SeriesGuide sqlite alternative

SeriesGuide X Pass

Dorian: Do you think the complaints came mostly during the shift from free to some paid features?

Uwe: Yes. In the beginning some people were upset, but as I only made convenience features paid, it wasn’t a huge issue. That is also a takeaway for me: don’t have a free app and then suddenly make half of the features paid, because then users will get upset. I was very careful to only make new or some convenience features paid. Or when I made the previously free theming features paid, I made an effort to spruce them up before. But features like notifications and server syncing were new and weren’t available for free before I implemented them.

Dorian: Do you have any tips for developers that are starting with their Open Source projects or are thinking about open sourcing their code?

Uwe: The best thing you can do for your project is to Open Source it, or in short: put it on GitHub. If you don’t put it online, people won’t find it. Another good way to get traction is to contribute to other projects so people know you exist. And then if you ask for help or feedback about their library you are using in your project, people will get to know your project and maybe look at it. Contributing is a good way to get into the community and be noticed. Give and be given, right?

Dorian: Now we have some fun fact questions. First, what do you think about Microsoft’s acquisition of GitHub?

Uwe: I don’t really care, because Microsoft has done some great things for the Open Source community. Azure runs Linux now and they have their own Linux operating system. It’s still good to know that there is the Open Source alternative GitLab that people can switch to if needed. However, it’s sad that things get monopolized into those big companies. In the end, we are maybe going to end up with only Microsoft, Google and Amazon. GitHub sold out, but we’ll have to see what happens.

Dorian: Do you have a favorite book, film, or game?

Uwe: I’m currently reading the Expanse series, which is also on TV. But my favorite series is the Culture series from Iain M. Banks. That blew my mind. For TV, there’s so many options. I generally like science fiction. I recently watched Killjoys and Altered Carbon which were both really interesting. Star Wars Rogue One is my favorite recent movie. If you want to know what I’m watching, follow me on Trakt.tv, a tracking service similar to SeriesGuide, but web-based, that SeriesGuide also integrates with.

Thank you Uwe Trottmann for the interview, and thank you for reading! 

If you enjoyed this open source interview, sign up for our newsletter! We are going to be conducting more interviews like this with Open Source Developers.

We would like to point out that SeriesGuide is not affiliated with ObjectBox

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Top 5 reasons why edge computing is crucial for IoT

Top 5 reasons why edge computing is crucial for IoT

IoT is growing at a very rapid rate and with it the vast amount of data it produces. Handling these amounts of data is an unresolved challenge. Edge Computing could be part of the solution

According to Dave Evans of Cisco, in 2010 the number of IoT devices connected to the internet passed the world population, with a device to person ratio of 1.84.1 By 2020 there will be up to ten Web-connected devices per person, collectively producing over 40 zettabytes of data.2, 4 

The graph on the right shows the estimated number of IoT devices from 2015-2025, Statista Gmbh.5 

Downsides of pure cloud computing in IoT use cases

Today, most IoT devices constantly push all data generated to the cloud and use little of the on-device capacities. There are some downsides to that:


  1. Data security
    When data is constantly being sent from device to the cloud, the risk of the data being compromised is huge. “As a centralized resource out of users’ control, the cloud resents an ever-present opportunity to violate privacy.”3 
  2. Realtime requirement
    IoT applications have a “need for speed”.2 The response time, however, inevitably decreases as the distance between device and the place where data is stored and computed (in the cloud) increases.2
  3. Cloud costs
    Pushing, storing, and processing all data in the cloud is associated with high cloud costs. These costs increase as data volumes increase.15

  4. Wastefulness
    Our current bandwidth infrastructure does not support this rapid growth: “With global Internet traffic growing by an estimated 22% per year, the demand for bandwidth is fast outstripping providers’ best efforts to supply it”.Even worse, most data stored in the cloud is of no value to the company and never used.

That is why analysts predict data will move to the edge. 2, 6, 10, 11

What is edge computing?

While there are varying definitions, a simple pragmatic definition is: computing data close to where it is produced, at the edge of the network, instead of a central point far away.1, 9 More technically, it is decentralized data persistence that happens on or near the devices that produce the data.

Moving data to the edge does not mean that data will be solely stored on the edge instead of the cloud. There is just a shift to more data being processed on the edge and less data stored in the cloud.1

Advantages of Edge Computing

Storing and processing data locally on device (e.g. on the IoT gateway) has some advantages:


  1. Privacy and Security
    If you are working with sensitive personal data that is not needed centrally / on the cloud, it is easier to keep data secure by storing it where it belongs.18 This can also ease up on GDPR compliance.12

  2. Latency / Speed
    If the data is being stored and processed in a local database, then computing can be done in real time rather than having to communicate back and forth with the cloud for every interaction.5 

  3. Offline-capability
    The more you compute on the edge, the more your app is independent from a constant network connection.19

  4. Costs
    Because you only store the data that is needed centrally or the data you really want to backup, your cloud costs will go down.12

  5. Resourcefulness
    Storing and processing data on the edge and only sending out to the cloud what will be used and useful saves bandwidth and server space.18

Practical Examples

Currently the main focus industries for IoT Edge Computing are Smart Cities, Autonomous Vehicles; Drones, and Industrial IoT.17

A simple case for an IoT edge solution is wearable health monitors. They locally analyze data like heart rate or sleep patterns and provide recommendations without the need for a constant cloud connection.16 It makes sense to be able to get health recommendations in any situation, no matter if there is an internet connection available. Also, not every patient may want all his/her personal health data stored online.
Straightforward IoT use cases, which can only work with local data processing, are (semi-)-autonomous cars. Data needs to be processed in real-time and independent of a network connection as no one would like to crash, because of lagging. Also, edge computing enables cars to process more sensor data faster and find patterns.5 
There is a trend to move data to the edge

When you look around the internet, you will find many studies predicting the rise of edge computing, for example: Peter Livine, partner at Andreessen Horowitz, predicted “the end of cloud computing” in favor of edge computing. Livine believes that the bulk of processing will soon take place at the device level.13 Transparency Market Research (TMR) forecasted the global edge computing market will be worth US $13.3 billion by the end of 2022.14 The IDC’s Global IoT Decision Maker Survey showed that 43% of IoT decision makers want to build on edge computing.4

For us edge computing makes a lot of sense, because it is resourceful, efficient, and data stays where it belongs. That’s why we built ObjectBox. Everything else, we’ll see… 😉


ObjectBox is a data storage and sychronization solution for IoT-devices (10x faster than any alternative, across devices from sensor to server, 1 million+ entities/second400kb native core, cross platform compatible, ACID-compliant). 


[1] Cisco (2011) https://www.cisco.com/c/dam/en_us/about/ac79/docs/innov/IoT_IBSG_0411FINAL.pdf
[2] Ieee (2018) http://innovationatwork.ieee.org/how-edge-computing-will-drive-5g-technology/
[3] Usenix (2015) https://www.usenix.org/system/files/conference/hotcloud15/hotcloud15-zhang.pdf
[4] IDC (2017) https://www.ge.com/de/sites/www.ge.com.de/files/IDC%20MarketScape_Worldwide%20IoT%20Platforms_Software%20Vendors_US42033517%5B1%5D.pdf
[5] Data Makes Possible (2018) https://www.datamakespossible.com/edge-computing-transform-autonomous-cars/
[6] IDG (2017) https://www.idgconnect.com/abstract/28926/iot-set-push-computing-edge-2018
[7] Scientific American (2016) https://www.scientificamerican.com/article/the-bandwidth-bottleneck-that-is-throttling-the-internet/
[9] Gartner (2017) https://www.gartner.com/smarterwithgartner/what-edge-computing-means-for-infrastructure-and-operations-leaders/
[10] Business Insider (2016) https://www.businessinsider.de/edge-computing-in-the-iot-forecasts-key-benefits-and-top-industries-adopting-an-analytics-model-that-improves-processing-and-cuts-costs-2016-7?r=US&IR=T
[11] Ieee (2016)  https://spectrum.ieee.org/tech-talk/telecom/internet/popular-internet-of-things-forecast-of-50-billion-devices-by-2020-is-outdated – as always with predictions. However, talking to many CTOs of IoT companies, we see there definitely is a need for edge computing.
[12] IoT Agenda (2018) https://internetofthingsagenda.techtarget.com/blog/IoT-Agenda/Living-on-the-edge-Why-IoT-demands-a-new-approach-to-data
[13] Andreessen Horowitz (2016) https://a16z.com/2016/12/16/the-end-of-cloud-computing/
[14] Transparency Market Research (2017) https://www.transparencymarketresearch.com/edge-computing-market.html
[15] SysGen (2017) https://sysgen.ca/cloud-vs-in-house-servers/
[16] Gartner (2017) https://www.gartner.com/smarterwithgartner/what-edge-computing-means-for-infrastructure-and-operations-leaders/
[17] Bowery Capital (2016) https://bowerycap.com/blog/insights/4-impacts-edge-computing/
[18] Hubraum (2017) https://www.slideshare.net/hubraum_iotacademy/edge-computing-and-5g-a-powerful-digital-mix-for-iot-ait-83646157
[19] HPE (2018) https://www.hpe.com/us/en/insights/articles/iot-analytics-strategy-cloud-edge-or-both-1803.html

Key Ideas to Empower Women in the Tech Industry

Key Ideas to Empower Women in the Tech Industry

Highlight-Women in Tech Panel at Droidcon Berlin 2018

Meet the speakers

This year at droidcon Berlin 2018 during the interactive day we were lucky to have the opportunity to host the Women in Tech panel. Our panelists had some very interesting things to say and we wanted to share the highlights. From left to right: Dr. Vivien Dollinger LinkedIn (ObjectBox), Annyce Davis LinkedIn (Off Grid Electric), Anita Singh LinkedIn (Winnie), Lara Martin LinkedIn (Babbel), and Kevin McDonagh LinkedIn (Novoda).

 “Free beer and ping pong doesn’t work for everyone” – Anita Singh

Women need equal pay in the workplace and companies should be more public with those numbers. There is a need for proper management training and women have left companies because managers don’t know how to adequately deal with discrimination and bias.
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“Being a mother helps you prioritize things and gives you a new perspective” “If you want something done give it to a busy person” – Annyce Davis

Being a mother helps you prioritize things, be more organized and empathetic at work, and realize that just as your own children are all different, so are your employees. The customers as well are all different and having that motherly insight can help reach a broader customer group.

“I had to look for role models” – Lara Martin

I remembered looking for blog posts of people doing career changes as I wanted to. I found one written by a woman who moved to Berlin and successfully started an iOS development career. The article gave me reassurance that I was capable of changing career paths and succeeding as well.
Feminism empowerment equal opportunity technology tech women female droidcon android
women in tech droidcon berlin 2018 moderator diversity equal opportunity

“Companies might still need to go the extra mile to enable gender equality in the future.” – Vivien Dollinger

For example, last year’s Techstars London class was the first class that was nearly 50/50 male and female CEOs. Max Kelly (MD) achieved this by searching actively for female founders, going the extra mile to diversify the program.

“Men should be feminists; I am one!” – Kevin McDonagh

It is easier for women to be in the tech industry in big cities such as London, New York, and San Francisco, but in other places, women have more problems fitting into the stereotypically male industry. There must be effort to changing company culture and to offer equal opportunities to both genders. In the current tech culture, men are heard more, so men must take the initiative to speak out about this issue.

General summary

The panel engaged in a lively discussion about women’s experience in the Tech industry from their personal experiences, and how the industry can adapt to better support women and families. Annyce Davis and Vivien Dollinger believe that gender equality needs to start early with children’s books showing less gender bias and inspiring girls with tech role models. Bringing in the male perspective, Kevin McDonagh identified himself as a feminist and encouraged more boys and men to embrace feminism. Anita Singh and Lara Martin talked about the women role models that inspired them to pursue a career in the Tech Industry, including Kalpana Chawla, the first woman of Indian origin in space.

We had a wonderful time hosting the Women in Tech panel, and we would be thrilled to make it an annual tradition – we already have new panellist ideas! If you would like to get in contact with us about the panel, message us on Twitter, Facebook, or LinkedIn.

women in tech droidcon berlin 2018 moderator diversity equal opportunity

Daniela Gausmann  Panel Moderator LinkedIn – Angel List profile  Download her presentation: 2018-Womenintech-Panel-PDF

Thank you for your support!

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Droidcon Berlin Women in Tech Panel 2018

Droidcon Berlin Women in Tech Panel 2018

We are looking forward to the Women in Tech panel at droidcon Berlin. It will be taking place during the Interactive Day on June 25th from 3:00-3:45PM.

The numbers show, there is still a lack of diversity in technology in both the startup world and the established tech industry. We are very excited to have successful women from the technology industry in different fields joining the panel to discuss reasons, implications, and possible solutions. Also, everyone from the audience is invited to participate in the discussion and suggest discussion questions upfront; don’t be shy 🙂

Key questions will include: What the current barriers facing women in the technology industry are; if and why diversity in the tech industry could be important, why moms can be great hires, and why role models are important to inspire girls to enter the world of technology. We’ll also go “meta” and discuss whether there even should be discussions about this and what the merits and risks of the ongoing discussion could be. We are going to be exploring these through the perspectives of both, the employer and employee.

And now, the

Women in Tech Panelists:

Annyce Davis droidcon women in tech off grid electric Amsterdam Netherlands

Annyce Davis–Android Development Manager at Off Grid Electric

Annyce is an Android Google Developer Expert, with a special focus on the Kotlin programming language. She has spent the past 7+ years developing applications for the Android ecosystem across multiple form factors. She is also an international conference speaker and author, sharing her knowledge of Android development with others.
LinkedIn Twitter GitHub


Lara Martin Carretero droidcon women in tech panel Babbel

Lara Martin–Junior Android Engineer at Babbel

Lara is a self-made Android developer based in Berlin. Her passion for Android made her transition from her background in science to software development. She’s currently part of the mobile team at Babbel and her dream is to make apps more accessible for everyone. When she’s not attending a tech meetup, you will find her on videogames.
LinkedIn Twitter GitHub


Kevin McDonagh droidcon women in tech panel Novoda

Kevin McDonagh–CEO at Novoda

Kevin is developing the world’s most desirable mobile products. He has developed for print, web, desktops and mobile and can confirm that they all take a long time to do right. He is an engineer on a journey of learning & growth. Kevin is a Scottish artist making light at Bryden Art.
LinkedIn Twitter GitHub


Vivien Dollinger ObjectBox CEO women in tech panel droidcon

Dr. Vivien Dollinger–Co-Founder and CEO at ObjectBox

Vivien has spent the last 15 years scaling teams in the mobile and gaming industries. After leading a successful app development business, Vivien cofounded ObjectBox in 2015. Leveraging a PhD in Economics, she manages the growth and development of the company as CEO. 
LinkedIn Twitter GitHub


Anita Singh droidcon women in tech panel Winnie San Francisco

Anita Singh–Senior Android Engineer at Winnie

Anita Singh leads mobile development at Winnie, an early-stage startup helping parents navigate the world with their kids, where she built the Android app from scratch as a solo developer. She transitioned from backend to mobile almost four years ago and is passionate about making Android development more approachable through blogging and speaking.
LinkedIn Twitter GitHub


Let’s dive into the iOS World

Let’s dive into the iOS World

Two days ago, we attended the Swift Lighting Talks Meetup in Munich for the very first time. We had beer, pizza and listened to Sebastian Sellmeier’s presentation on making programming accessible and Denis Grebennicov’s presentation on the process of developing a Document Scanner app. It was fun and very instructive, thanks!

We also gave a 15 minute sneak peek talk about our ObjectBox iOS binding. Markus covered the basics of ObjectBox before sharing how we managed to overcome iOS constraints in our APIs. Finally, he disclosed the first (early) performance benchmarks on iOS, which we think are quite encouraging…

Check out the full talk in the video below.

In case you want to learn more about ObjectBox on iOS, sign up here for news and Early Access.
Special thanks to Stefan Mayer-PoppThe Munich iOS Developers Meetup for organizing this event and to Mayflower for hosting it.


We officially released our YouTube channel, we will post videos about ObjectBox and Tech in general. Subscribe to stay tuned.