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I find the pricing and logic errors that quietly cost travel companies revenue — before they reach customers or decision systems. As the sole data-validation analyst on a travel loyalty-optimisation platform, I've independently QA'd a loyalty-and-pricing engine with 100,000+ rules, validate hundreds of fares daily, and build the calculation models that confirm an app's output matches real-world earning and pricing behaviour. WHO I HELP Travel-tech teams, loyalty platforms, OTAs and airline-programme tools that depend on large, fast-moving pricing and earning data they need to trust. WHAT I DO - Competitor price monitoring across multiple travel sites - Fare and award anomaly detection (Deal / Flash Deal / Phantom Fare classification) - Independent calculation models that verify airline status, earning and pricing logic - Large-dataset verification, QA workflows and continuous data-consistency testing - Python data pipelines: API ingestion → PostgreSQL → analytics → dashboard HOW I BUILD IT I design end-to-end pipelines that pull live fares from the Amadeus and Duffel APIs, store append-only price observations in PostgreSQL, classify deals against rolling baselines, and gate every alert through a QA verification step before export. The result: clean, trustworthy data instead of false signals. TOOLS Python (pandas, SQLAlchemy, pipelines, automation) · PostgreSQL · SQL · Google Sheets · Excel · Amadeus & Duffel APIs · Streamlit · Docker · ETL A recent client put it simply: "Stefan helped us set up and test our complex logic system with over 100,000 rules — no small task." If you have pricing or loyalty data you can't fully trust, tell me what's breaking and I'll tell you how I'd validate it.

worked as an administrative assistant in a chemical plant for five years. Data entry, internet research, Google Sheets, and PDF manipulation were all part of the job, alongside English to Serbian translation of leaflets, user manuals, labels, and product descriptions. Two years of experience working as a data analyst for DataFox improved my skills in data manipulation even more through various tasks. Most of the work was to identify errors within company records inside a database and quickly and efficiently research and process quality data. I have advanced knowledge of English and Photoshop. Experienced UpWork jobs: Translation/subtitling Data entry Copy/Paste jobs KDP Amazon books uploading Data (spec) tagging Data scraping Company information research

As an applied mathematician I have a review on how to apply tools of mathematics to solve different problems. My specialised fields are mathematics in finance, probability, statistics, and optimization. I can use different programming languages for solving problems. I am the most familiar with Matlab, Python and R Studio. At university, I always chose optional subjects related to informatics and data science. In such a way I reached the knowledge of data science and data analyses using the programming language Python. I could get out interesting and relevant from big sets of data using program packages Pandas, Statistics, Numpy, and so on. These results should help people to make a better decision. I have experience in developing databases in Microsoft Access. My biggest project was the creation of a database for Organisation "Sunce" from Novi Sad where I was employed. With SQL queries and user-friendly design, I could develop a database that is easy to use for getting relevant information. My other interest is graphics design. My finished course in graphic design significantly contributed to my designing skill. I am specialized for design business cards and posters in Photoshop. You can also find some three-dimension models that were made in Sketchup. Feel free to contact me for any potential projects.

Top Rated Plus top 3% of Upwork talent | 250+ satisfied clients | 9+ years of experience Academic writer and editor: PhDs, master's theses, honour's theses, Q1 and Q2 papers Data analyst: R, Python, SPSS, STATA, PowerBI, Tableau | Survey & experimental data, Business reports, UX research, A/B testing, Econometrics, Biostatistics, Medical data, Text analysis, and much more. I always deliver excellent work, on time, and with the possibility of explanations and modifications. You can always reach me (within 6-8 hours at most), and I will make sure you are satisfied with my work every step of the way.

Experienced and detail-oriented professional specializing in data management and analysis. Passionate about software engineering and technology, with a strong aptitude for learning and adapting quickly. A highly skilled and motivated Data Analytics Specialist with expertise in managing and analyzing large volumes of financial data, employing ETL processes and Python programming. Excels in transforming raw data into actionable insights and delivering effective solutions. Proven ability to collaborate with cross-functional teams, contribute to organizational success and communicate effectively in English

I'm very focused and responsible. I'm looking for perfection. I'm very interested in sports. Also i like to read and write articles about animals, nature, movies etc. I barely make mistakes, and i check everything few times. I'm a very communicative person and and I am easy to cooperate about anything. I used to work for travel booking app Hopper, on project called Analysis on Price Competitiveness for Online Travel Agency - Daily Project, from January 2024 to August 2025. I like to stay in touch with the people I worked for. It is very important for me that my employer is satisfied with me.