Senior Performance Test Engineer

CSHARK; Wrocław; Hybrid; PLN 180,000 - 240,000; Full time

Benefits offered by this job

Flexible hours

International projects

Charity actions

In-house technology workshops

Remote-first culture

Job summary

CSHARK is seeking a Senior Performance Test Engineer to own performance testing across an international project. You will drive the process from requirements and test-data preparation to execution, analysis and final recommendations, using k6 scripts and modern tooling.

You will craft workload models, test REST APIs, and parameterise tests in Azure DevOps Pipelines, while evaluating results with Prometheus and Grafana. Strong English and cross-functional collaboration are essential.

Qualifications

• Proven experience in end-to-end performance testing.
• Strong knowledge of k6 scripting, checks, metrics, and thresholds.
• Ability to design performance scenarios from business requirements.
• Experience testing REST API flows with authentication and data correlation.
• Familiarity with Azure DevOps Pipelines for running and parameterising tests.
• Practical experience with Prometheus and Grafana for performance analysis.
• Experience in preparing and validating test data for performance testing.
• Ability to translate requirements into meaningful workload models and acceptance criteria.
• Strong analytical and troubleshooting skills to identify bottlenecks.
• Experience with AI tools to support testing while validating outputs.

Responsibilities

• Own performance testing end-to-end from requirements to final reporting.
• Design performance scenarios with transactions per hour, load tiers, and acceptance criteria.
• Select k6 workload models and executors for different scenarios.
• Test REST API flows including authentication and data correlation.
• Prepare/validate test data and CSV feeders.
• Run and parameterise tests in Azure DevOps Pipelines.
• Analyze performance metrics with Prometheus and Grafana.
• Correlate client-side results with infra metrics.
• Identify bottlenecks and root causes of failures.
• Prepare evidence-based recommendations for stakeholders.
• Coordinate testing activities across multiple teams.
• Leverage AI tools to assist script development and analysis.

Skills

Performance testing

k6 scripting

Azure DevOps Pipelines

Prometheus

Grafana

REST APIs testing

Test data preparation

AI tools usage

English language

Git

Tools

esbuild

Git

Job description

We are looking for a Senior Performance Test Engineer to take ownership of performance testing within an international project.

In this role, you will drive the performance testing process end to end — from understanding business requirements and defining workload models through preparing test data and k6 scripts to test execution, results analysis and final recommendations.

We are looking for someone who does more than simply run performance tests. You should be able to understand what the results actually tell us — determine the practical performance ceiling of a system, identify potential bottlenecks and distinguish infrastructure issues from application errors, test-data problems or issues within the test scripts themselves.

Your Daily Missions

• Owning performance testing end to end — from requirements and test-data preparation through execution, analysis and final reporting.
• Designing performance scenarios based on business requirements, including transactions per hour, load tiers and acceptance criteria.
• Selecting appropriate k6 workload models and executors for different performance scenarios.
• Testing REST API flows, including authentication, sessions and data correlation between individual steps.
• Preparing and validating test data, including CSV feeders and sensitive data.
• Running and parameterising performance tests through Azure DevOps Pipelines.
• Exporting and analysing performance metrics using Prometheus and Grafana.
• Correlating client-side test results with application and infrastructure metrics.
• Identifying bottlenecks, practical performance ceilings and root causes of failures.
• Distinguishing between script, test-data, application, infrastructure and environment issues.
• Preparing clear performance reports and evidence-based recommendations for both technical and non-technical stakeholders.
• Identifying risks and blockers early and proposing appropriate mitigation.
• Coordinating performance-testing activities across Development, DevOps, QA and business teams and working closely with the Project Manager and Release Manager.
• Using AI tools to support script development, test-data preparation, log and result analysis and reporting while critically validating generated output.

The Essentials We’re Seeking

• Strong hands-on experience with performance testing and independently driving performance-testing activities end to end.
• Strong practical knowledge of k6, including scripting, check(), metrics and thresholds.
• Solid understanding of k6 workload models and executors and the difference between VU-based and arrival-rate-based approaches.
• Strong experience testing REST APIs, including HTTP methods, headers, session-token authentication and data correlation between requests.
• Ability to interpret HTTP and application-level error codes and identify the actual source of performance-test failures.
• Hands‑on experience with Azure DevOps Pipelines, including running and parameterising tests, variables, conditions, artifacts and dedicated agents/pools.
• Practical experience with Prometheus and Grafana, including performance-metric analysis and correlation.
• Experience preparing and validating test data for performance testing.
• Ability to translate business requirements into meaningful performance scenarios, workload models and acceptance criteria.
• Strong analytical skills, including identifying bottlenecks, determining practical performance ceilings, and distinguishing degradation from hard performance breaks.
• Strong troubleshooting skills and the ability to distinguish between script, data, application, infrastructure and environment issues.
• Experience producing clear performance reports and evidence‑based recommendations without overinterpreting results.
• Ability to take ownership of the performance‑testing area and coordinate activities across multiple teams and dependencies.
• Practical experience using AI tools to support performance‑testing activities combined with the ability to critically validate AI-generated output.
• Basic knowledge of Git and feature‑branch workflows.
• Strong written and spoken English, used comfortably in an international, cross‑functional environment.
• Experience working in closed or isolated environments without direct internet or npm access.
• Experience building and running prebuilt bundles, for example using esbuild.
• Experience performance testing banking or fintech systems.
• Experience with multi‑country systems and country‑specific configurations.
• Familiarity with user onboarding and authentication flows, including registration, verification, login and session management.

The Quality Assurance Team brings together diverse skills and experience levels to enhance standards in software development. With a collaborative ethos, the team promotes knowledge sharing and mentorship. Upholding a ‘Support Over Blame’ philosophy, we value learning from mistakes and encourage open discussion. Emphasizing continuous learning, the QA Team stays updated on industry trends. Our team stands out with its tailored approach, ensuring adaptability, agility, and innovative client‑centric solutions.

At CSHARK, it’s not about trendy perks or the latest gaming console in the lounge. Based on feedback from our team, what truly counts is an environment conducive to focused work, structured processes, and continuous skill development. We prioritize what genuinely enriches the daily work experience, ensuring that every moment spent with us is both productive and fulfilling.

Harness the power of technology with our remote‑first approach. Work from the comfort of your space while staying connected and collaborative.

Flexible hours

Find your rhythm with hours that align to your lifestyle. We understand that productivity isn’t confined to the typical 9‑to‑5.

International projects

Engage in projects that transcend borders. Experience the thrill of working with diverse teams and clients from different parts of the world. Navigate the global tech landscape with ease. Enhance your communication skills with our tailored Business English sessions.

Navigate the global tech landscape with ease. Enhance your communication skills with our tailored Business English sessions.

Participation incharity actions

Connect with the community and contribute to causes that matter. Join us in various charity initiatives and be apart of change that extends beyond business.

In-house technology workshops

Stay at the forefront of technology. Dive deep into topics, refine your skills, and learn from peers through our regular tech workshops.

Explore theHeartbeat ofCSHARK

Discover the essence of our guilds’ expertise, advanced tools and tech stack, and our real‑world successes. Delve into impactful case studies and hear genuine insights from our team.

Wondering about our organizational vision, the executive leadership team, the values we passionately uphold?

Explore our diverse portfolio to witness a blend of pioneering financial ® regulatory solutions, next‑gen manufacturing, and innovation examples.