carrot.
Hi, i am back end developer (full big data and services)
I have a little team, we have knowledge how do to do anything you want.
I see you need many services with really high performance and full availability.
I recommend use a compiled language like to Java or Scala (two betters on performance in the last time for web and services development) if we want find information on much page we will need index that on a NoSQL database, with a queue system on real time like to kafka, additionally we can add support with kafka and ElasticSearch to do the query requires, we have too many ways to do that for this reason we need know many information (maybe is needed integrate with hadoop).
I think the development is easy, but we will need high performance and really good technologie. Aren't good idea if we try use PHP, Ruby on Rail, NodeJS (i like nodejs but no to develop this ) or SQL technologies(MySQL, PostgreSQL, Oracle, and others). we will need good performance.
We really need technologies with Big Data support, by this reason i i suggest this.
I think in total we can require around 25000 USD to do the project on 4 or 5 months, this with full features.
This include the 3 natives APPS mobiles.
This is my simple proposal, have good day and bye.
Thanks by your time.