ZeroSSL project

I participated in the ZeroSSL project as a member of the development team while working for Stack Holdings GmbH. My contributions to ZeroSSL were software development as well as business development related.

As ZeroSSL rapidly grew development team had to make sure our software ran smoothly, and we had to resolve legacy code and scalability issues.

Interesting topics

Integration between ZeroSSL and Zendesk notifications

At the time, we used Zendesk for customer support, tickets, escalations, and maintenance notifications. What became a problem is that information was present only within Zendesk environments. Website users would need to learn about expected maintenance windows or ongoing issues. Users would heavily strain support; many tickets were generated because customers weren’t informed.

The solution was to integrate Zendesk with ZeroSSL and ensure customers see important notifications in multiple places within our product.

We reused existing integrations and extended them to support ZeroSSL. With adequately planned storage and caching, we ensured minimum API pressure when fetching data from Zendesk while being able to refresh often enough for our customers to be timely informed.

The results were fantastic; the system was working as expected. The customer success team could quickly spread its message to all our customers. Developers had an easier time planning maintenance windows. Support ticket numbers were reduced, especially for maintenance windows and outages. With all these benefits, there were no additional costs.

Database performance improvements

With constant customer base growth, we recognized weak points in DB queries. It is expected from growing products because scalability mechanisms are rarely in place in the initial development and growth phase. We investigated problematic DB queries, discovered bottlenecks, and found safe ways to improve performance without affecting end-user experience.

With these efforts, we ensured that the steady growth of ZeroSSL could continue while also reducing pressure on our servers. In addition, this optimization resulted in both stability and cost optimizations.

Designing, implementing, and evaluating KPIs for ZeroSSL with company CFO

Together with the company CFO, we designed and implemented KPIs for the ZeroSSL product. As a result, we could track sales growth, user retention, referral activities, customer lifetime values, etc. KPIs helped us make informed decisions.

This side-project also sparked interest in data-driven decisions throughout the company. Sales and marketing teams started relying on our data even more. This activity also resulted in an initiative to invest more time and research Business Intelligence (BI) opportunities.


ZeroSSL is an online service that enables SSL certificate creation and management. It allowing users to create website security certificates issued by ZeroSSL. Certificate management can be done via UI or ACME integrations, or using a full-fledged SSL REST API.

My roles: Senior Software Engineer

Impact: New features; Improved Security; Improved Scalability; Legacy code improvement; Maintenance; KPIs design, measurement and evaluation; Database optimization