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Why (and how) to migrate your app from Amazon MWS to SP-API?

Amazon MWS to SP-API Migration Guide 2022

The upcoming Amazon API revolution is changing the way we integrate with its marketplace. If you are an Amazon seller using software to improve your sales, manage your inventory, optimize your listings or reprice your items with AI, you should give this change a closer look!

The history of Amazon Marketplace Web Service (MWS) can be traced back to 2002, and since then, was used by developers to communicate with external software and apps. Nevertheless, the reign of MWS is coming to an end in 2023, as that's when every single app and script will have to migrate to the newest SP API.

In this article, we will show you why and how to migrate your project from the MWS to SP API based on our experiences working with similar projects. Whether talking about a custom script or an old legacy project that you no longer use or you no longer have the documentation for - we got you covered. We will walk you through the whole migration process and try to answer your most essential questions - what is it about, why should you care, and what does it look like?

So, what is the MWS and Amazon SP API?

MWS and SP API comparison

Amazon MWS, called Amazon Marketplace Web Service, was used for the last 20 years. If you were ever using some software as an Amazon Agency or Seller it was probably using the old MWS to connect to the Amazon Marketplace.

MWS deactivation deadline

Recently Amazon started pushing toward the new Selling Partner API, which is a suite of JSON-based REST APIs. It's modern and very well-documented compared to MWS so whenever you are building new software you should use SP-API. Since the first parts of MWS will become deactivated on July 31, 2023, the migration is urgent - since if you rely on any software based on the old Amazon MWS it might be that literally within a day your business and its operations might collapse. In short - by mid-2023 your app should be up and running using SP API.

Who should migrate to the SP-API?

You have to migrate to the SP-API when you:

  • use a third-party (public) application to connect to Amazon's MWS;
  • use a private application to connect to Amazon's MWS;
  • are an Amazon Vendor and would like to access your Amazon data via an API for the first time.

What does the migration look like?

MWS to SP-API migration in 5 steps

Step 1: Analysis - analyze current code and logic.

Step 1: Code and logic analysis

Let's assume we work on migrating an old MWS script built in Python to SP-API. How do we start? The first step is to analyze the code, which we can do even without extensive documentation by diving deep into the code. Here we essentially try to understand what the old developer had in mind and double-check the old MWS documentation to make sure we understand the logic behind the script.

Step 2: Optimization - simplify and optimize the logic (e.g. batch requests, better infrastructure, production code).

Step 2: Logic optimization

The next step is simplifying and optimizing the logic. If something was built in the wrong way in the past we shouldn't simply rewrite it with the new technology. We sit down and think of how we can improve and optimize the algorithm's complexity. Thanks to that, the modernized version of your script will work much faster and become more efficient.

In those projects the most important parts to focus on are:

  • algorithmic complexity;
  • allocations and copies;
  • memory access and cache performance;
  • the number of instructions;
  • production code;
  • infrastructure.

Step 3: Expansion- add new features/integrations if necessary.

Step 3: Adding new features to your old Amazon MWS app

Migrating your MWS app to the new SP API is the best time to think about its new features and integrations. You might have simply outgrown your old app and now require more data and features. In this step we can, for example, create new integrations with other Amazon marketplaces (such as Amazon Germany or the UK) or connect with entirely different marketplaces such as eBay or Walmart. And we can do all that while rewriting the app's logic.

You might also decide to create a web application from your script with a friendly UI/UX for you and your clients, so you can analyze all of your data through a set of user-friendly dashboards.

The other idea is to create additional scripts to scrape additional data that is not provided by API and sync it with your databases.

Step 4: Technical Documentation - write technical documentation of the project.

Step 4: Writing the technical documentation of your new SP-API based app

If you have a legacy code and a project that already went through many different phases of development it could become a bit messy. This is a great time to invest a bit more time and create extensive technical documentation of your project. This will allow every new developer to smoothly jump in, learn about its logic, and develop new features with ease. 

Step 5: Development - code a new, better version of the app/script.

Step 5: Coding a new, better version of your old Amazon MWS based app

The last, and most exciting step is to code a new, better version of your app or script. This is, obviously, the most complex part because here we build everything from scratch using the newest APIs and creating unique features based on the technical documentation we previously put together for you.

A great example here is a project made for one of our clients from Ohio. For him we created a solution that can:

  • automatically scan and analyze products from Amazon;
  • fully optimize & handle the restocking process;
  • includes a warehouse & Amazon inventory management system;
  • handle replenishments to Amazon FBA.

You can read more about this particular project here:


We can make your MWS to SP-API transition easy!

We hope that with this short guide, the whole MWS to SP-API migration process became much clearer. If you need help with it, we got you covered! 

  1. Fill out the form on our website or message us directly at
  2. We will schedule a call and identify the project's scope.
  3. Once we determine its essential functionalities and goals, we will get back to you with an offer within the next few days.
  4. Once you make up your mind, your dedicated Project Manager will guide you through the rest of the process - from ideation to the final implementation.

Make sure to check out the video version of this guide on our Youtube channel, where our co-founder Jakob will guide you through the whole process:

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