Which aws zone to choose if website traffic will be from india only

I am running a website whose traffic is totally from India only and tested various options.

If the traffic is from India only, just go for Singapore Zone in Asia Pacific region.

The latency from their is minimum and will vary somewhere around 70-120ms (measure from Delhi, India).

Though you would have to pay some extra bucks comparative to N. Virginia Region, but it's worth it.

The latency from N. Virginia region will be somewhere around 250-350 ms.

The Amazon AWS availability zones are listed here. This list can be updated at any time, so this is a snapshot.

If you're serving traffic to India, it makes sense to place your systems in the Asia Pacific availability zone, if for no reason than latency. The path to Northern Virginia is far more complex, and you'd be bypassing the European Union region, which would be a better choice than anything in the United States.

AWS now have a region on Mumbai.

I am performing the same tasks as you, where the traffic is 100% from India. I have chosen Ireland over Mumbai/Singapore/Sydney because Ireland has more AWS services available. For example, if I want to use EFS, none of the Asia Pacific regions offer it, also Developer services like CodePipeline is not available in Mumbai.

You can use Mumbai in the entirety, provided you use the equivalent services (like S3FS or GlusterFS instead of EFS).

Also, there is a cost factor. Mumbai is exorbitantly high compared to any AWS region. Just feed the site on Ireland and setup a CloudFront to serve traffic in India.