Updating a dynamoDB table (incrementing an integer) using transactions in lambda - node.js

Question

I'm trying to update the follower-count for two items in a dynamoDB table using node.js 12.x. Here is my code:
const AWS = require('aws-sdk');
AWS.config.update({region: "us-east-2"});
const dynamoDb = new AWS.DynamoDB.DocumentClient();
exports.handler = async (event) => {
const followingUser = "#FRIEND#"+ event.queryStringParameters.followingUser;
const followedUser = "USER#" + event.queryStringParameters.followedUser;
const followedMetadata = "#METADATA#" + followedUser;
const followingMetadata = "#METADATA#" + followingUser;
const followingUsername = "USER#" + followingUser;
const current_time = Date.now();
console.log(event);
try{
const response = await dynamoDb.transactWrite({
TransactItems: [
{
Put: {
TableName: "rememoriesDBv2",
Item: {
"PK": followedUser,
"SK": followingUser,
"followedUser": event.queryStringParameters.followedUser,
"followingUser": event.queryStringParameters.followingUser,
"timestamp":current_time
},
ConditionExpression: "attribute_not_exists(SK)",
ReturnValuesOnConditionCheckFailure: "ALL_OLD"
}
},
{
Update:{
TableName: "rememoriesDBv2",
Key: { "PK": { "S": followedUser}, "SK": { "S": followedMetadata} },
UpdateExpression: "SET followers = followers + :i",
ExpressionAttributeNames: {"followers": "followers"},
// UpdateExpression: "ADD followers :i",
// ExpressionAttributeNames={'followers': 'followers'},
// ExpressionAttributeValues: {":i": {"N": "1"}},
// UpdateExpression: "set followers = followers + :i",
ExpressionAttributeValues:{ ":i": {N: 1}},
ReturnValuesOnConditionCheckFailure: "ALL_OLD"
}
},
// {
// Update:{
// TableName: "rememoriesDBv2",
// Key: { "PK": followingUser, "SK":followingMetadata},
// UpdateExpression: "SET following = following + :i",
// // UpdateExpression: "set following = following + :i",
// ExpressionAttributeValues: {":i": 1},
// ReturnValuesOnConditionCheckFailure: "ALL_OLD"
// }
// },
]}).promise();
}
catch(err){
console.log(err)
}
// TODO implement
const returnValue = {
statusCode: 200,
body: JSON.stringify(event.queryStringParameters.followingUser + " is now following " + event.queryStringParameters.followedUser),
};
return returnValue;
};
I've been running into problems the entire time, but here is the current error:
INFO ValidationException: ExpressionAttributeNames contains invalid key: Syntax error; key: "followers"
at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:683:14)
at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)
at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)
at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:685:12)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:116:18) {
code: 'ValidationException',
time: 2020-07-31T15:34:22.073Z,
requestId: 'B6NJ2EC686PFVBFE0P4MVFBB17VV4KQNSO5AEMVJF66Q9ASUAAJG',
statusCode: 400,
retryable: false,
retryDelay: 47.858884374085854
}
I've also gotten this error:
INFO ValidationException: Invalid UpdateExpression: Incorrect operand type for operator or function; operator or function: +, operand type: M
at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/protocol/json.js:51:27)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:683:14)
at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:22:10)
at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)
at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:38:9)
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:685:12)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:116:18) {
code: 'ValidationException',
time: 2020-07-31T14:19:56.774Z,
requestId: 'ROQC1RTQTD4784CK8JBQ47FKKBVV4KQNSO5AEMVJF66Q9ASUAAJG',
statusCode: 400,
retryable: false,
retryDelay: 31.52114733740706
}
Ultimately, I'm unable to find much AWS documentation, and am not sure where to go from here. If anyone could help me find out what exactly is going on with my code and what is wrong with it, it'd be greatly appreciated.
Here is the table schema
It then has random elements depending on the type.