lambda task timed out error while using rekognition - amazon-web-services

Question

I'm building a React native app with serverless framework using AWS services.
I created a RESTapi with lambda function (nodeJs8.10 environment) and API gateway to use rekognition services such as indexFaces, listCollection, etc. My lambda is in VPC with RDS( later I'll Aurora) to store faceID and other data.
Everything works fine except rekognition services.
When I call any rekognition services it shows Task timed out after 270.04 seconds.But it works when I call locally using serverless-offline-plugin
I attach all necessary permissions to my lambda like AmazonRekognitionFullAccess
Here is my code
index.js
app.post('/myapi', function (req, res) {
var params = {
MaxResults: 3,
};
const rekognition = aws_config(); <-- rekognition configuration
rekognition.listCollections(params, function(err, data) {
if (err) {
res.json(err.stack);
console.log(err, err.stack);
}
else{
res.json(data);
console.log(data);
}
});
});
function aws_config(){
const $options = {
'region' : 'ap-southeast-2',
'version' : '2016-06-27',
'accessKeyId ' : config.ENV.aws_key,
'secretAccessKey ' : config.ENV.aws_secret,
};
return new AWS.Rekognition($options);
}
How to solve this timeout error as it doesn't show any error on CloudWatch logs?