As of September 2017, you no longer have to configure mappings to access the request body.
All you need to do is to check '**Use Lambda Proxy integration**' under 'Integration Request'.
**Note:** If you change it, don't forget to deploy your API gateway again.
You will then be able to access your query string params this way :
event['queryStringParameters']['val1'] event['queryStringParameters']['val2']
For more details try to return your **event** object as a response of your Lanbda function and you'll find all the informations (headers, body, query params etc) returned when your Lambda is triggred.

As of September 2017, you no longer have to configure mappings to access the request body.
All you need to do is check, "Use Lambda Proxy integration", under Integration Request, under the resource.
[![enter image description here][1]][1]
You'll then be able to access query parameters, path parameters and headers like so
event['pathParameters']['param1'] event["queryStringParameters"]['queryparam1'] event['requestContext']['identity']['userAgent'] event['requestContext']['identity']['sourceIP']
[1]: https://i.stack.imgur.com/P3ctm.png