You need an experienced programmer who knows social networks

You need an experienced programmer who knows social networks.
Required:
1. Write new functionality for the site, new sections and modules
2. Fixing many errors related to changing the social networking
3. Write different apis to link bot and Android/ios applications
4. Redesign the structure and principle of the site
5. Optimize the site to reduce the load
6. And so on.

Definitely:
1. Payment in parts as work is done
2. Experience with high-load systems
3. Experience with social networks, api social networks
4. Knowledge in the following areas: html5, css3, php7, mysql, JavaScript, memcached, redis, mongo database
5. Be able to write/change rest api (api for the relationship between bot and applications)
6. Be able to understand self-written engines, quickly delve into the work of the site, write various scripts
7. Optimize the engine under load, reduce load
8. Experience of 6 years or more

It is desirable, but not necessary:
8. Experience in setting up CentOS 7 x64 servers
9. Be able to work in Text hidden
10. Optimize the server under load
11. Long-term cooperation
12. No one and people from Moscow should write.
13. Leave your Skype. I'll answer tomorrow.

Website engine: self-written.
Operating system: CentOS 7 x64