Unable to handle promise rejection with mongodb and mongoose - node.js

Question

I have the following code, that basically skips the mongodb document entry stage if the incoming documents are already in the database. However this function causes an UnhandledPromiseRejectionWarning when trying to close the db connection immediately after the async is complete.
async dbInsertMany(asset, timeframe, stream){
try{
const [currentAssetModel, multiStream] = this._getMultiModel(asset, timeframe, stream);
// Don't run the db stage if zero length stream received.
if(!multiStream.length==0){
// Refactor this into a try..catch..finally block.
try{
await currentAssetModel.insertMany(multiStream);
console.log('<SUCCESS>');
}catch(err){
console.log('<ERROR>', err);
}finally{
console.log('__DBINSERTMANY:FINALLY__');
};
}else{
// await sleep(1000);
console.log('[WARNNING] No unique documents to add.');
}
}catch(err){
throw new Error('Application failure has occurred!');
}
}
I'm not sure what I'm missing.
The functions that follow are below:
async function dbCycle(){
try{
let asset = new AssetDatabaseHandler();
try{
await asset.dbInsertMany('BTC/EUR', '5m', demoMultiExchangeStream)
console.log('DB_INSERT_MANY: Finished.');
}catch(error){
console.log('DB_INSERT_MANY: [ERROR]', error);
}
}catch(failure){
console.log('[SEVERE_FAILURE]', failure)
}
};
and
(async () => {
try{
await dbConnection.dbConnect();
console.log('Connected.');
const result = await dbCycle();
console.log('> Finished.');
}catch(err){
console.log('> Failed.', err);
}finally{
// dbConnection.dbDisconnect();
console.log('Disconnected.');
}
})();

Answer 1

The .exists() method is returning a promise, something I have overlooked. Waiting for the promise to be resolved after the query is sent fixed the problem. Because I was not waiting for the promise and closing the server for cases where there was nothing new to be added to the db, the orphaned promises were causing the unhandled exception. Something like the code below, solved the problem:
async checkStates(stream, model){
let state;
let states = [];
for(const item of stream){
const date = new Date(millisecondsToTimestring(item[0]));
const ISODate = date.toISOString();
state = await model.exists({date: ISODate});
states.push(state);
// console.log(item, date, state);
}
return states;
}