Take a look at some of our clients’ testimonials:

I highly recommend Lev Selector as an effective and responsible professional.

Lev Selector has worked at Appnexus as a consultant for almost two years (May 2012 – April 2014). He has automated our billing processes and created a foundation for daily reporting systems. His project was a solid success despite difficulties of development during times of fast, turbulent change. Lev also successfully worked with multiple groups inside the company, and with me personally to improve our operational processes.

Brian O'Kelley

CEO, AppNexus

To whom it may concern,

I am writing to recommend Lev Selector as a very experienced and productive lT professional.

Lev was originally invited to work at AppNexus as a consultant in May of 2012 to automate some manual operations, which were taking many days of several employees.

Lev successfully solved this problem.

Lev was able to create effective algorithms, reducing execution time in some cases from hours to minutes. Lev is an effective programmer and also has a Ph.D. in mathematical modeling. He was very helpful in creating multiple reports for the Finance department.

Lev is very good at sharing his expertize. He has trained new employees.

Lev is very hard working and devoted to the success of his project. Lev’s contract was extended several times because of his exemplary performance.

Lev works very quickly. He is very consistent and productive. He can plan and organize his work (doesn’t need micro-management). He has performed well under pressure of tight deadlines, multiple last-minute changes, and numerous data problems. Our company owes him big debt of gratitude, especially for his readiness to put effort and extra hours when it is really needed.

Overall Lev’s work was a success. I highly recommend Lev as someone who can find simple effective solutions to seemingly complicated problems, and who can implement them really fast.

Igor Shindel

CIO, AppNexus

To whom it may concern:

It is a pleasure for me to write this letter of recommendation
for Lev Selector.

Lev is a very talented and hard-working IT consultant. He worked on my team from May 2012 through December 2013. During this time, Lev created a foundation for our billing and revenue-reporting infrastructure. He originally joined us to automate a largely manual billing process, and created an application that allowed us to reduce the process from several days to less than an hour.

Based on his success, Lev’s contract was extended and he continued to develop the system and data structure to improve the system capability and data quality. He also incorporated multiple checks and tests into the process.

Lev became our “go to guy” on billing, and was always ready to share his knowledge, always ready to help others, and worked
well under pressure of tight deadlines.

I highly recommend Lev to anyone who needs to solve complex IT problems.

Bruce Cooperman

CFO, AppNexus

I worked with Lev as a senior-level specialist working within our Data Warehouse team on several projects related to processing of huge web data sets. Lev worked on the design of the database and data-streams, implemented database loaders and data conversions.
I recommend Lev as a very experienced and effective python / database programmer and architect. Not only is Lev very skilled at his job, technically, but he’s extremely passionate about doing the right thing for the project and organization and takes time to think about how technical decisions will impact business outcomes. He also served as somewhat of a mentor to a more junior person in my team, teaching him extremely valuable Python skills that have allowed us to create much more useful internal reports for stakeholders.

Erica Curtis

Vice President, Campaigns & Analytics, Penguin Random House

As Lev’s direct manager at Penguin Random House, I recommend him highly. Lev was originally with us for a short-term contract, which we were able to extend several times. In addition to his contributions in the area of Python/ETL software development and analytics, Lev has been a great teacher, often taking the initiative to research and recommend new tools, and helping teammates to solve problems and learn best practices in Python, Pandas and other technologies. Lev is a one-of-a-kind person, highly motivated, highly skilled, and always thinking about ways to make things better, and ways to help the team. It has truly been a pleasure working with him.

Dan Christian

Director of Data Warehouse Development, Penguin Random House

I worked closely with Lev for the past few months as a primary consumer of the data pipelines he worked to implement. He is indeed a vocal advocate for functional programming and for the use of python, but he is also tirelessly committed to enabling a project’s success. In my experience, this latter passion trumps the former. He was a critical component to several key strategic projects, internalizing project requirements quickly and working tirelessly to find a way to execute them. His deep knowledge of and experience working with data in python will be sorely missed.

Jacqueline Novik

Biostatistician, Icahn School of Medicine at Mount Sinai

Lev is a Python wizard and he was a wonderful colleague during our acquaintance at Penguin Random House. His machine-code-level knowledge of the routines underneath several key Python libraries in the scientific programming stack impressed us all, and his design and code contributions to our ETL jobs helped to improve their speed manyfold. In addition, he left behind several useful programming paradigms / best practices that are now in use throughout our code base. He is careful and delivers under pressure — truly an expert.

Justin Boelio

Senior Data Scientist, Penguin Random House

I would highly recommend Lev with whom I have worked directly for three
years at Goldman Sachs and again for an additional year at Credit Suisse. During this time I have witnessed Lev’s obsessive quest for knowledge and his devotion to Technology, Marketing and Finance. Any tasks assigned to Lev will be completed in a timely fashion and usually he will offer alternate improved solutions which may have otherwise been missed. It has always been a pleasure to work with Lev and he comes highly recommended.

Roger Hall

Vice President, Morgan Stanley

I unreservedly recommend Lev as an asset to any team. In his time with PRH IT Applications, I’ve come to know Lev as insatiably curious, unbounded in his range of interests, skilled in his professional tools, and dogged in pursuing solutions to problems he encounters. He is not a passive, inbox-clearing automaton; rather, he is entrepreneurial and approaches challenges with a holistic vision.

Very quickly, Lev established a reputation for innovation in his work and good cheer in his relationships. In short: he classes up a place.

Robert Landry

Senior Analyst, Penguin Random House

I worked with Lev in the same team on a Python big-data project. He was always very pleasant to work with and always ready to help — very important, since I was new to the company and he was an old hand.
He is a very experienced, knowledgeable, and effective programmer, with expert knowledge of Unix/Linux, Python, shell scripting, and databases, as well as mathematics and analytical algorithms.
I highly recommend him.

Fred Bartlett

Senior IT Analyst, Penguin Random House

I’m very happy to be able to Recommend Lev as an excellent addition to any software engineering team. I had the pleasure of working along side of him and others managing a portfolio of Data Ingestion and Modeling Projects, and was frequently impressed with his ability to deliver complex analytics capabilities through Python and other database programming. More importantly, though, Lev is always willing and knowledgeable enough to go above and beyond his individual responsibilities in order to provide time-saving and efficient suggestions that benefit the team as a whole.
Specifically, the projects we worked on involved cleaning, processing, and loading millions of rows of web-collected data for analysis in a data warehouse. Lev’s suggestions on loading, and subsequently processing and testing this data, as well as his substantive individual contributions were greatly valued and will be greatly missed! They reduced load times and made more efficient use of system resources, and resulted in testing processes that will more efficiently generate results.
Beyond that, his encouraging attitude and genuine care for his colleagues makes him a pleasure to work with.

George Kantor

Director, Strategic Projects, Penguin Random House

I was Lev’s manager for the majority part of Lev’s work in AppNexus. I highly recommend him for the following reasons: he’s excellent at what he does; he’s a great teacher; he’s a caring person.

Lev was initially hired for 3 months of work to build a billing system. He was so good at the job that we kept extending his contract and it lasted two years. He built the billing system with breakneck speed and excellent quality. Later, he expanded that system into analytics and reporting. In addition, he did a lot of work in ERP integration.

Lev is very generous in sharing knowledge. He taught Python to many people in AppNexus. He designed an effective teaching method that all his students benefited from.

Lev is one of the most compassionate person I’ve met. It was truly an honor to get to know him.

Lev thrives in an environment that values taking initiatives and being accountable for one’s work. If you have work that requires a smart and experienced programmer who has great attention to details, Lev is the best choice.

Jennifer Jihui Yang

Senior Manager, Financial Analysis and Analytics, AppNexus

Lev is very detailed oriented engineer and can count on him anytime including critical time. He’s very thorough in following up on any dependencies and focused on getting it done on time & budget. He worked on a very complex billing system at AppNexus from the ground up. He handled the knowledge transition very well and trained the team in all the required areas. I enjoyed working with Lev as an Engineer and a Manager.

Ben John

Software Engineering Leader, AppNexus

I had the pleasure of working with Lev during his tenure as a consultant on the Financial Analytics team at AppNexus from April 2012 to April 2014. For those who aren’t familiar with AppNexus, we auction display and mobile ads in real-time, processing billions of transactions per day. Each billing cycle, these billions of transactions are rolled up to produce actual invoices for clients. Lev’s primary responsibility was to produce these invoices, ensure their correctness, and, when necessary, work with folks on our data, product, and finance teams to address any anomalies in this data.

Lev’s attention to detail, strong work ethic, and high regard for delivering correct invoices on time made our invoicing process *much* smoother and more reliable. Lev also did a nice job integrating tools into his workflow that AppNexus engineers favor, including Pandas and iPython notebooks. These tools allowed Lev to move fast, and also made on-boarding other engineers onto this team easier during Lev’s eventual transition period out of AppNexus.

On a personal note, I always enjoyed hearing Lev’s latest programming tribulations, as well as his thoughts on life in general. Lev Selector is a good man, a stellar programmer, and a good friend, and I would recommend him for work in any technical organization, but especially one that demands attention to detail and high regard for customer satisfaction.

Joseph Huttner

Software Engineer, AppNexus

I have been working with Lev for the last year or so. He is a consultant whose contract was repeatedly renewed. Lev is a great guy. Personally and professionally. Lev is a brilliant analyst and programmer. His specialty is python, but quite frankly, he programs in many languages and environments. Lev is very astute and insightful, and his intelligence comes out in his work. Lev’s background is in math, technology, and physics. He is quite brilliant.

Lev is also a great guy to talk to, about anything. He is well-read and has many interests. His family is pretty cool, too. Lev has been a colleague and a friend. I cannot recommend anyone more highly.

Andrea Hollander

Programmer, Penguin Random House

Lev is one of the most brilliant engineers I have ever worked with in my entire 30+ year career. His grasp from fundaments and advanced technologies all the way up to the business models is insanely deep. His solutions are both pragmatic and innovative. Lev has always delivered under budget and on time. As important, he has always been hardworking yet modest and has always been a valuable team member. And finally, when he leads, he does so in a respectful and productive manner with constructive criticism that leaves all of us feeling that he is one of us.

Luther Günther Quick III

Architect & Software Engineer, Barclays

Lev was hired as a database consultant for a research infrastructure project, JDS, in JPMorgan. Lev delivered a lot of high-value functionality. Lev’s Sybase and Perl skills are top-notch. He performed a lot of “expert” tweaking of our queries to provide very fast searches across large data sets (800K+ rows across multiple tables). Lev is easy to work with, and possesses a high-degree of knowledge in Sybase, Perl and algorithms. His “expert” knowledge allowed us to deliver the necessary performance for our high-profile project. I would recommend Lev to any project that is trying to solve complex, challenging problems.

Johnny Wu

Business Analyst, JPMorgan Chase

Lev was a consultant on the project that I was leading at JPMorganChase. He was responsible for all data loading and data management tasks. Lev was very diligent and detail oriented. His code was always optimized, well structured, and well tested. He was a pleasure to work with.

Diana Bruk

Technical Lead, JPMorgan Chase

I know Lev as an expert in variety of modern technologies used in large scale web-sites and big data projects in financial or online advertising sectors.

Lev is out of the box thinker and provides targeted solutions surpassing expectations in quality and time of delivery. I had the pleasure of working with him on several projects in financial and marketing industries, where he showed his acumen and great results, adding clearly defined value to the projects.

I also found him a great team player, able to flexibly navigate and judiciously contribute to various team and client-related solutions, which was an added benefit of having him on the same team.

I cannot recommend him higher and would definitely work with him again given an opportunity

Alexander Voll

Business Technology Architect, TD Securities

I’ve worked with Lev on several data integration and processing projects over the past year. Lev is not only extremely experienced and technically knowledgeable, he is also passionate about the work he does and enthusiastic about sharing his knowledge base with others. Lev personally worked with me to improve my Linux, Git, Python, Pandas, and other technologies, and was instrumental in teaching me many skills I now use every day. He has been a go-to person for both specific code questions and best practices. I highly recommend Lev to anyone who needs an effective senior software engineer and analytics person.

Delano Scott

Manager, Analytics Operations, Penguin Random House

Lev and I both worked for the Data Warehousing group at PRH and from Day One I was impressed by his expertise in Python, as well as his ability and willingness to share that knowledge. His Python tips have already served me well.

Michael Gordon

Data Warehouse Developer/Analyst, Penguin Random House

Lev was a wonderful coworker during my time with him at AppNexus. He had profound knowledge of handling complex data and was a great help to my team. He was able to simplify demanding tasks from multiple groups while meeting and exceeding the tight deadlines in a fast-changing environment. I would highly recommend Lev for all future opportunities.

Carson Kwan

Senior Billing Analyst, AppNexus

Michael Rakhman worked for me while in AppNexus. He is very diligent and detail-oriented. He also took the initiative to research things on his own and used the knowledge in his work.

Jennifer Jihui Yang

Senior Manager, Financial Analysis and Analytics, AppNexus

I worked with Michael Rakhman on a survey analysis project and was extremely happy with the results. Michael was able to perform all data cleaning, analysis, and presentation with minimal help and with great attention to detail. I enjoyed working with Michael and I highly recommend him as a data analysis professional.

Gil Dror

Director of R&D, Fung Global Retail & Technology

Lev is very good and brilliant programmer in perl/unix. His coding techniques are well documented and easy to understand. I strongly recommend him as a good architect/programmer in Perl/Unix.

Subray Shetty

Data Warehouse Architect, AppNexus

Lev is extremely good at his job, and also very willing to teach. He was instrumental in building AppNexus’ billing system, and is a highly organized coder. Lev’s approach to problems is systematic and precise.

David Yang

Financial Analysis and Planning, AppNexus

Lev is a talented programmer with a knack for understanding big data. He encourages everyone around him to improve tasks through automation and he leads that front by example. In my opinion, his greatest strength is his ability to simplify complex tasks. I strongly recommend Lev and his work.

Andrew Lee

Business Operations Analyst, AppNexus

Lev is a very energetic and a determined colleague. He is passionate about evangelizing python and has been actively promoting it within the organization.
He convinced his teammates to use python for a number of data processing tasks and to my knowledge they’ve successfully implemented several of the data transformations and load tasks in python and cython.
Due to his efforts even a few people outside of his team are aware of python and the data manipulation packages (ie. pandas) and have a favorable view of the python ecosystem.

Alex Asinovski

Contract Senior Software Engineer, Penguin Random House

I like working with Lev for the following major reasons:
1) He is proactive and always deliver what is promised
2) His deep knowledge of technology stack saved us a lot of time and money
3) He has excellent communication skillsMerrill Lynch

Оleg Аyupоv

Sr. Consultant / DB Architect, Merrill Lynch

I worked with Lev Selector for approx. 1 year in 2002, when we both were consultants at Goldman Sachs. I remember Lev as very knowledgeable, experienced, accurate and persistent in his work. He also had a good sense of humor. I would definitely highly recommend Lev both as a dedicated professional and as a very good person to work with.

Julia Sibula

Sr. Business Analyst, Morgan Stanley

Lev Selector is an extraordinary person in all areas where he works. He has a talent of fast learning and teaching. His ideas are always original and brilliant. I am really thankful to Lev for everything that I learned. He would be a great contributor for any complicated project.

Ludmila Borovikova

Manager, Zodiac Interactive