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Zdravko Kosanovic
Verified Expert in Engineering
Back-end Developer
Belgrade, Serbia
Toptal member since November 15, 2022
Bio
Zdravko is a senior back-end engineer with over seven years of experience in various industries, from telecommunications to fintech. He's proficient in Go and has extensive experience working with cloud providers such as AWS, GCP, and Azure. Zdravko loves solving problems in a distributed cloud environment and architecting and developing microservices.
Portfolio
Microsoft
Microsoft Azure, C++, C#, Windows PowerShell, Windows
Rise
Go, Kubernetes, Docker, Redis, PostgreSQL, BigQuery, Amazon Web Services (AWS)...
Rain
Go, PostgreSQL, Redis, Apache Kafka, Heroku, Docker, Microservices, SQL...
Experience
- Docker - 7 years
- Amazon Web Services (AWS) - 7 years
- Go - 6 years
- Microservices - 4 years
- Redis - 3 years
- PostgreSQL - 3 years
- Apache Kafka - 2 years
- gRPC - 2 years
Preferred Environment
MacOS, GoLand, Docker, GitHub, Amazon Web Services (AWS), NeoVim Text Editor, Tmux
The most amazing...
...thing I've developed with my team is a complete digital platform and infrastructure for one of the biggest telecommunication operators in South America.
Work Experience
Software Engineer 2
2025 - 2025
Microsoft
- Developed core infrastructure components for Azure Compute services, supporting millions of virtual machines across Microsoft's global cloud platform.
- Contributed to an internal infrastructure testing platform by developing and maintaining e2e tests.
- Participated in cross-functional developer experience initiative to implement workflow improvements, resulting in measurably increased team satisfaction scores and enhanced developer productivity.
Technologies: Microsoft Azure, C++, C#, Windows PowerShell, Windows
Back-end Developer
2022 - 2024
Rise
- Managed the Rise SSP platform that serves 1+ million requests per second.
- Maintained Rise adapter on Prebid.js and prebid-server open source libraries.
- Led cost-reduction projects that cut the operating expenses of the platform by more than 70%.
- Wrote technical guidelines, held knowledge-sharing sessions, and mentored more junior developers.
Technologies: Go, Kubernetes, Docker, Redis, PostgreSQL, BigQuery, Amazon Web Services (AWS), Amazon RDS, Terraform, Amazon S3 (AWS S3), Amazon EKS, Amazon Elastic Container Service (ECS)
Senior Back-end Engineer
2020 - 2022
Rain
- Built Rain Pro, an advanced trading platform for experienced cryptocurrency traders.
- Ensured 99.9% uptime of both Rain Core brokerage and Rain Pro trading platforms.
- Developed several tools and 3rd-party service integrations to help Rain's growth, marketing, and customer experience teams reduce user churn and speed up growth.
Technologies: Go, PostgreSQL, Redis, Apache Kafka, Heroku, Docker, Microservices, SQL, Distributed Systems, Relational Databases, Back-end, Back-end Development
Software Engineer
2019 - 2020
Symphony
- Created a digital life insurance platform as part of the Symphony team working as a contractor for a US-based startup.
- Owned several core services within the microservice architecture after fully integrating into the client's engineering team, handling new features' development, testing, and monitoring.
- Oversaw the platform's stability and availability, ensuring 99.9% uptime.
Technologies: Go, Protobuf, gRPC, PostgreSQL, Google Cloud Platform (GCP), Kubernetes, Docker, Microservices, SQL, Distributed Systems, Relational Databases, Back-end, Back-end Development, DocuSign
Software Engineer
2018 - 2019
LotusFlare
- Contributed as part of the server team building LotusFlare's core product, the Digital Network Operator platform, a next-gen software stack for telecom operators.
- Engaged with the team in designing and developing the platform's features and creating its most successful operator-specific deployment at the time.
- Oversaw and supported the platform we built from scratch and saw it grow from zero to having over five million daily active users.
Technologies: Scala, Java, Lua, Amazon Web Services (AWS), Apache Kafka, Docker, Redis, Apache Cassandra, ClickHouse, Jenkins, Prometheus, Microservices, Distributed Systems, Back-end, Grafana, Back-end Development, Amazon S3 (AWS S3), Python
Experience
Rain Pro Platform
Rain Pro is a powerful and advanced trading platform designed for experienced cryptocurrency traders.
It was built as an evolution of the then-existing, simple, brokerage-based trading model of the Rain crypto exchange.
It was built as an evolution of the then-existing, simple, brokerage-based trading model of the Rain crypto exchange.
LotusFlare DNO Platform
https://www.youtube.com/watch?v=_UteggVyoiUDigital Network Operator (DNO) is a telecommunications platform that lets operators deliver an excellent and fully digital mobile experience. I worked as part of the server engineering team designing and developing the platform from scratch, up to its multiple successful deployments.
DocuSign Integration for a Construction Collaboration Platform
As a Toptal contractor, I led the complete development of a DocuSign integration for a document editing platform in the field of architecture and construction. Taking full ownership from project inception, I designed and built two production-ready microservices. I researched and integrated the DocuSign API with OAuth and delivered both services ahead of the deadline.
Beyond core development, I ensured production readiness through comprehensive unit testing, extensive functional testing, and detailed documentation for seamless front-end integration. I collaborated closely with the front-end team, architect, and product manager through daily standups and regular progress demos.
This integration addressed one of the client’s most requested features, enabling seamless document signing workflows. As the sole back-end engineer on this initiative, I delivered the complete solution in just three months, successfully bringing a high-priority feature to production on schedule.
Beyond core development, I ensured production readiness through comprehensive unit testing, extensive functional testing, and detailed documentation for seamless front-end integration. I collaborated closely with the front-end team, architect, and product manager through daily standups and regular progress demos.
This integration addressed one of the client’s most requested features, enabling seamless document signing workflows. As the sole back-end engineer on this initiative, I delivered the complete solution in just three months, successfully bringing a high-priority feature to production on schedule.
Skills
Libraries/APIs
Protobuf, React
Tools
Jenkins, Grafana, BigQuery, Terraform, Amazon EKS, Amazon Elastic Container Service (ECS), Tmux
Languages
Go, SQL, Java, JavaScript, C, Scala, Lua, Python, C++, C#
Paradigms
REST, Microservices
Platforms
Docker, Amazon Web Services (AWS), Kubernetes, Apache Kafka, Google Cloud Platform (GCP), Heroku, Windows, AWS Lambda
Storage
Redis, Relational Databases, PostgreSQL, NoSQL, ClickHouse, Amazon S3 (AWS S3), Amazon DynamoDB
Frameworks
gRPC, Windows PowerShell, OAuth 2
Other
Distributed Systems, Back-end, Back-end Development, Apache Cassandra, Prometheus, WebSockets, Amazon RDS, DocuSign, Microsoft Azure, OAuth, APIs, NeoVim Text Editor
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