Instant and feeless transactions plus smart contracts?

[arcassis]

I have a daunting project (a marketplace) with lots of micro-transactions and micro-interactions.
I want to store and validate those micro-transactions and micro-interactions on the blockchain so that I would provide the highest degree of trust to my members.
Before I invest tens of hours in studying the overwhelming offer of technologies, can you guide me to one of the best alternatives for what I'm looking for:
1. instant and feeless transactions
2. smart contracts

kindly thank you

[Vikhy]

I donno if x42 is what you're looking for, It's feeless, is PoS has smart contracts/side blockchains.More info on my signature.