Industry Expertise

By combining domain knowledge with technical expertise, Callista has helped its partners to bring innovative products to market and scale up their businesses. With a full-stack development team and DevOps partners we offer a one stop shop for all your technical and business development needs.

Logistics IT

Banking IT

Industry 4.0

Healthcare IT




Product Strategy & Architecture

In conjunction with your product owner, our team iterates on your business plan and product design to help you succeed. With vast amounts of experience in SaaS and PaaS solutions, we can offer valuable insights and propose a plan of action, to achieve and exceed your goals!

Back-End Development

The back-end is your source of truth. Our team of experienced Java and PostgreSQL developers ensures the highest level of quality. By performance benchmarking and automating the testing process we can provide a scalable and fault tolerant service.

Technology Audit

Businesses evolve over time and some services and processes get lost or are forgotten. That can hinder further development and scaling efforts. To make informed decisions you need a clear picture. This is where our experts come in to help you map your existing solutions and propose a way forward.

Scaling & Cloud Native Software

Modern software solutions need high availability and scalability. By partnering with us, you get access to a team of experts to design and implement your infrastructure. Whether it is on Amazon, Google Cloud or a custom Kubernetes cluster — we got you covered!

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Case Studies

Callista helps international corporations as well as small startups to build, ship and scale amazing software products. You will find some of our recent case studies below:


Refactor existing monolith into microservices and improve scalability.

The amount of new customers and data flowing in is hitting the limit that the existing solution can process. There are stability challenges at peak hours and redeployment is complex. Due to the monolithic nature of the software, monitoring separate data flows is difficult.


Our team analysed the existing software solution and chose a path of careful refactoring, one module at a time into a separate service. Due to the requirements of keeping the existing system live at all times, we employed black box end to end testing to validate each change to the system and had rollback mechanisms in place. By iterating this process, we separated the existing monolith into 8 separately scalable microservices and improved the throughput, monitoring capability, separation of concerns and data integrity.

  • Throughput benchmarked at 10x over the previous system
  • From one deployment in 2018 to 4 in 2019;
  • 75 incidents in 2018 to zero in 2019;
  • Investment payback period of less than one year.
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Contact Details

Callista Software OÜ
+372 5017268

Veerenni 38
10135 Tallinn,
Estonia, EU
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Callista Software OÜ
Reg code 12287975
VAT no EE101789916