Introducing Spaces

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Published by Marius Sprenger on June 25, 2021

Hi there! My name is Marius, and I am part of a (still) small, but highly motivated team that is building, an easy-to-use API that lets you develop your own brokerage product at the stock market. In this blog post, I want to introduce you to the concept of Spaces. Read on if you want to learn more about the specific Space functionalities and why we think that the concept facilitates and improves the developer experience for our users.

lemon markets spaces

When we launched our first prototype last year, a line of feedback that we most frequently received from our users was the wish to be able to test multiple different strategies simultaneously. While we offered the possibility to create different strategies and attach an access token to them, we noticed that this approach was not thought through to the end.


Well, simply because one bad strategy could affect the overall balance and therefore also all the other, potentially well-performing strategies. While time progressed and our users started building different projects, it became clear that this API structure really worsened their product experience. After a while, one prototype user told me:

So, I had these 3 really solid trading strategies. They were rather standard and made automated investment decisions based on quantitative analysis of previous historical stock prices using different buy/sell rules. Things were going great! And then I wanted to spice it up a little and went full experimental mode. Didn’t go so well, and my automated strategy bought way too many wrong stocks at the wrong time. Actually, it went so badly that the profits I made from my other 3 solid strategies were completely gone as well.

This story made us think. Even more when other users mentioned similar problems that led to losses on their side. Obviously, you cannot always control everything and stock prices going up and down is part of the game, but what bothered us was that there was no way to actually limit your risk. So, we discussed it internally when we designed the new API structure and came up with (well, you probably guessed it): Spaces.

If you look at the graphic below, you will hopefully understand how our new API is structured:

You as a user have one total balance. Speaking in API terms, this is called your “state”. Think of your state as a place where your unused money is stored. In our closed beta, we transfer €100,000 of paper money into it. In the future, you will be able to transfer real money from a bank account of your choice to an additional “real money state”.

However, once you want to actually build something, you will need to create a new space and deposit a certain amount of money into it. Let’s say you create Space 1 and deposit €5,000: your total balance would then be €95,000 (meaning you have €95,000 left to deposit to new spaces) and you would be able to use the €5,000 in that space for whatever you like. Once you’ve created a space, you can start building. We automatically create a default client for you with which you can then request an access token, but you can also create customised clients on your own. However, these are all technical details that go beyond the scope of this blog post, but we’re nevertheless excited that you will get to try them out soon!

lemon markets dashboard spaces

This is how your Dashboard will look like in action. You can find all of your Spaces in there.

So: why are Spaces a good idea again?

Well, first of all it is a feature that directly emerged from the feedback our community gave us and which hopefully solves a direct problem for them. We strongly believe that a great product can only be developed in close collaboration with the users, especially when it’s such a customer-centric one as

With Spaces, we are offering you more flexibility for your trading product. A Space allows you to build a specific trading use case, as you have the chance to deposit a specific amount of money into it and then use it only for your specific project. This:

  1. leads to a better overview, as you can monitor each project in isolation and rigorously monitor its development, and
  2. limits your overall risk, as only the Space the project is built in (and the money in there obviously) will be affected.

We hope you got a good glimpse of what we are trying to do with giving you the freedom to build any brokerage product you want. Building a reliable infrastructure for that takes time, and we do not want to rush things and then end up with a mediocre product experience. Therefore, we are carefully rolling out our closed beta right now, onboarding small batches of users from time to time to receive valuable, personal feedback by developers that have an intrinsic motivation to help shape (and who are forgiving/patient when some things are not yet working perfectly and stay loyal nevertheless 😉).

If you haven’t done it, yet: sign up for our waitlist or contact us at [email protected].

We are super excited to show to the public very soon 🍋 🎉

Have a good day,

Marius from

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