Application overview

This repo is a solution for technical interview challenge by Valpay. It uses serverless architecture lambda, api gateway and dynamodb.

Prerequisite To Install and Deploy

*nix Destro Development was made on Ubuntu
Makefile sudo apt-get install makefile
AWS CLI
AWS SAM

Stake Deployment Command

Below Makefile command is an abstraction for a guided deployment

  make deploy

Sample sam deploy command input:

Setting default arguments for 'sam deploy':

 Stack Name [valpay]:
AWS Region [eu-west-1]:
Parameter Environment [dev]:
#Shows you resources changes to be deployed and require a 'Y' to initiate deploy
Confirm changes before deploy [y/N]: N
#SAM needs permission to be able to create roles to connect to the resources in your template
Allow SAM CLI IAM role creation [Y/n]: Y
#Preserves the state of previously provisioned resources when an operation fails
Disable rollback [y/N]: N
TransactionNotificationFun has no authentication. Is this okay? [y/N]: y
PayoutNotificationFun has no authentication. Is this okay? [y/N]: y
Save arguments to configuration file [Y/n]: n

Application Explained:

I've used NoSQL key/value pair DynamoDB Table with HASH key merchantId and RANGE key transactionId. Also with secondary local index which is used to generate reports and for query operation with RANGE key transactionDate.

The Table Structure is as follows:

merchantId (HASH), type String
transactionId (RANGE), type String
transactionDate (RANGE), type Number
type, type String valid values auth, refund or dispute
paymentTarget, type string valid values valpay or merchant
payouts, type Array

On PayoutNotification the payouts array is appended onto the pay value provided from the POST payload of the PayoutNotification webhook

The application folows method factory pattern which create objects of type or paymentTarget which are constructed using strategy pattern

The Architecture is depicted by the below diagram:

Limitations:

AuthZ/AuthN not implemented possible solution AWS Cognito service
SNS Notification on third party collection service failure not implemented, although stubs are there.