Jianfeng Wang, Developer in Sunnyvale, CA, United States
Jianfeng is available for hire
Hire Jianfeng

Jianfeng Wang

Verified Expert  in Engineering

Ad Serving Developer

Sunnyvale, CA, United States
Toptal Member Since
May 14, 2016

Jianfeng has over 10 years of experience as a full-stack engineer with a focus on back-end systems. He's worked at both big companies like Oracle, Yahoo, a few small startups, Adify, and GrowMobile. He has built scalable web apps, ad serving systems, and AWS management systems.



Preferred Environment

GitHub, Sublime Text, Ubuntu, MacOS

The most amazing...

...thing I've built is GrowMobile, from scratch to launch in 6 months. The system serves 100M daily requests, generating $10+M in revenue in the first year.

Work Experience

Funding Engineer, Core Developer

2012 - 2015
GrowMobile (Acquired by Perion)
  • Built the majority of the product from scratch before the acquisition.
  • Created the dashboard using Ruby on Rails to all advertisers managing campaigns, with reports for viewing. The UI is Twitter Bootstrap.
  • Developed the back-end with API integration to 100+ ad networks, an attribution server to track ad clicks, app installation, and real-time attribution. Used MongoDB as the data ingest store, and Vertica as a data warehouse for the reporting and analysis.
  • Managed 100+ servers in AWS and handled most operations including Bootstrap servers, deployment, monitoring, backup/restore MongoDB, and load balancing.
  • Built an RTB server using Go.
  • Created a mobile client SDK (Android, iOS, Unity).
Technologies: Amazon Web Services (AWS), MySQL, Vertica, Redis, MongoDB, Ruby on Rails (RoR), Ruby

Senior Engineer, Manager of Back-end System

2006 - 2010
Adify (Acquired by Cox)
  • Built portions of Adify, an ad-serving technology platform to power and service vertical online ad networks.
  • Designed and implemented a reporting engine including UI and back-end data pipeline.
  • Implemented a billing and payment system.
  • Implemented campaign/account management.
Technologies: .NET, SQL, C#

Lead Engineer

2005 - 2006
  • Designed and implemented a back-end framework for Yahoo! Health/Lifestyle property using PHP.
Technologies: MySQL, PHP

Lead Engineer

2000 - 2005
Siebel System (Acquired by Oracle)
  • Created a field service scheduler/appointment booking engine using C++.
  • Owned the assignment engine as a common component for entire Siebel vertical of applications using C++.
  • Built the field service dashboard module with Gantt chart to manual a schedule of field engineers.
  • Created parts of the Siebel Call Center application and the Siebel sales application.
Technologies: C#, Java, C++

SwordWind: Kids Safety Product on Android

Mobile App to track kids location, app usage, rule setting (school hours, total hours of app usage, permission on certain apps). Parents can view reports and receive alerts.


RealTime Video/Audio streaming from your Raspberry PI, based on WebRTC

Android Casual Game

Mobile Game on Android.
1997 - 2000

Master's Degree in Computer Engineering

Vanderbilt University - Nashville

1994 - 1997

Master's Degree in Eletrical Engineering

Tsinghua University - Beijing China


Git, Sublime Text, GitHub


Ruby on Rails (RoR), Bootstrap, Django, .NET


Python, Java, Ruby, C++, C#, PHP, SQL, Go


Linux, Android, MacOS, Ubuntu, Amazon Web Services (AWS)


Redis, MongoDB, MySQL, Vertica


Agile Software Development


Ad Serving

Collaboration That Works

How to Work with Toptal

Toptal matches you directly with global industry experts from our network in hours—not weeks or months.


Share your needs

Discuss your requirements and refine your scope in a call with a Toptal domain expert.

Choose your talent

Get a short list of expertly matched talent within 24 hours to review, interview, and choose from.

Start your risk-free talent trial

Work with your chosen talent on a trial basis for up to two weeks. Pay only if you decide to hire them.

Top talent is in high demand.

Start hiring