Martin Kostov
Software Architect @ DraftKings
Sofia, Bulgaria
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Martin Kostov is a software architect based in Sofia, Bulgaria, with 14+ years of experience designing and scaling distributed, data-intensive software systems.
His work focuses on AI-assisted software engineering, LLM-based systems, database performance, stream processing, cost optimization, reliability, and engineering leadership.
His talks and workshops are practical and case-study driven, aimed at senior engineers, architects, tech leads, and engineering managers who need to make better technical decisions under real production constraints.
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Workshop: Breaking the Testing Vibecode
The "happy path" is a lie—especially when there’s a Large Language Model involved.
Most AI implementations look great in a controlled demo, but they crumble the moment they hit
unpredictable user inputs or high-concurrency production loads. If you aren't actively trying to
break your AI-generated code, your users eventually will.
If you don’t know your system’s breaking point, the universe will assign one to you.
In this workshop, we will build integration and performance tests for a small distributed system.
We will explore integration tests:
1. How AI can make mocking parts of the system easy
If you can define the testing scenario, it will be built
2. Human in the loop and verification are very important for tests. 3. How can we utilize agents
to minimize the human-in-the-loop?
We will explore for performance tests:
1. What are the types of performance tests?
2. What are the best in-class performance testing tools?
3. How to build and maintain performance tests
Workshop Details
Participants will build integration and performance tests for a small distributed system.
Participants should have access to AI-assisted IDEs and plugins such as Claude Code, Cursor,
Copilot, Antigravity. Free tiers are acceptable as well, however best-in-class tools do make a
difference.
The workshop’s focus will be on building an AI agent that will assist in producing both integration
and performance tests.
Finally, the workshop will explore how these tests can be integrated into the SDLC
Mastering the Total Cost of Ownership of Software
Every line of code, every product roadmap decision, and every architectural choice has a price tag that extends far beyond the initial development effort. When choosing between competing features, how do you measure the potential Return on Investment (ROI) against the true cost?
In a competitive market, understanding and managing the Total Cost of Ownership (TCO) is not just an accounting exercise—it's a critical factor for survival and success. This workshop moves beyond theory to give you a practical framework for making smarter, more cost-effective decisions that drive real business value.
Goals
Participants will learn how to:
Identify the hidden costs in the software development lifecycle, from infrastructure and maintenance to team scaling.
Calculate and forecast the potential TCO of new features and technical changes.
Analyze the Return on Investment (ROI) of a feature by balancing its TCO against its projected value and revenue.
Challenge product requirements and design decisions through the lens of long-term value and cost.
Develop a data-driven mindset to balance innovation with financial sustainability.
Communicate with stakeholders - from Architecture Decision Records, Product Specifications, and Tech Plans, communicating the TCO requires a different approach depending on the audience
Reflect - every team will need to come to terms with when they succeeded, got lucky or failed.
Retrospectives are a powerful tool for learning and will be used in the workshop.
Process
This is a highly interactive, full-day workshop. The day will begin with a short exercise of buying a car when you have more money than the car costs, but you don’t consider the extra costs like insurance, new tires, extra space, and baby seats. Then it will continue with foundational concepts, using real-world analogies to frame the TCO mindset. The majority of the workshop will be a hands-on, team-based simulation.
Groups will be given a budget, a product goal, and a deadline. They will then make a series of strategic decisions, from hiring and technology choices to testing and deployment strategies. Each choice will directly impact their budget, and they will need to justify their spending by projecting the ROI of their decisions.
Every decision will involve risk—dice will determine if the rock star developer from the interview is the real deal or if the corners you cut for backups will be a bad dream or reality. The teams will also face the volatility of any developing market; Scalability requirements will change, so will requirements.
By observing the outcome of every decision, the participants will grasp that metrics such as “man days” or dollar amounts (like the price per year of a service) directly impact a business's bottom line.
The workshop will explore several frameworks for understanding the TCO impact of a feature such as Cost-Benefit Analysis, Systematic Edge Case Discovery strategies like FMEA and more.
The day will conclude with a group reflection on how the lessons and findings from the day can help the participants improve their work.
jsTalks Bulgaria 2024
jsTalks Bulgaria 2024 is a community event that will take place on November 22-23, 2024 at Innovation Forum „John Atanasov“. The conference is focused on the cutting edge .js technologies and future trends.
Co-speaker for one of the workshops of the event.
Leveraging Technology for Cost-Efficient Software Architecture
This session explores the intersection of software architecture and cost-efficiency, drawing insights from DraftKings’ transition to AMD EPYC processors. We’ll examine how technological choices impact both performance and operational costs in large-scale systems.
We will start by discussing the case study of DraftKings’ shift to AMD EPYC processors, focusing on the balance between performance and cost. The session will then delve into strategies for efficient Redis cluster management and how different hardware choices can influence key performance indicators. Lastly, we’ll engage in an interactive discussion on applying these principles to diverse software architecture scenarios.
Martin Kostov
Software Architect @ DraftKings
Sofia, Bulgaria
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