Android app mobile data sync between app and server

This project needs to synchronize the user application data on android mobile phone to the remote server and vice versa with compression to reduce the data traffic as much as possible. reducing the data traffic is No. 1 goal. Security is No. 2 goal. Initial data needs to be compressed before transmitting on each direction, i.e. upload or download. Only the incremental changes are allowed to transfer between mobile device and server after initial first setup. Data could be multiple files under one directory and of any format, i.e. txt, jpg, video, audio etc. all data transfer must be encrypted in transmission. directory could have sub directories. How the data is saved on local and remote is up to designer. Initial raw sample data can be provided. Server side needs to support 10000+ concurrent requests. phone client response is less than 3 seconds server response time should be less than 10 seconds. Data integrity check should be done by md5 on both ends. Compatible with major android phone models: Lenovo s960, Samsun SCH-N719, Xiaomi 2S, HTC Z715e etc. Client memory usage < 30MB, peak less than 60M Server memory usage < 100M, peak less than 200M client continuously runs 48 hours Server continuously runs 7x24. Standard Software engineering practice: documentation of architecture and design. source code with header description, testing framework maintenance requirements after delivery: 3 months free trial run support 1 year free technical support.