designing to overcome 3rd party API rate limits in firebase functions

My product tracks the user’s stock portfolio. I have created a Firebase function that is called every 24 hours. This function goes over the user’s stock data and makes a call to a 3rd party API to get the latest stock prices etc. My code used to work fine until recently when the API vendor imposed a max 5 calls per minute rate limit. Now, with the current code, I start getting failures after the first 5 calls. How do I re-architect my code to add this wait after every 5 calls I make? Below is what the code looks like

exports.dailyNetworth = onSchedule("every 24 hours", async (event:any) => {
  ...

   for(let uid of validUsers.keys()){
      const finColRef = db.collection("users/" + uid + "/finance")
      const fQuerySnapshot = await finColRef.orderBy("Date",'desc').limit(1).get()
      fQuerySnapshot.forEach(async(doc:any) => {
        let data:any 
        data = doc.data()        
          const finance = new Finance()
          finance.assets = data.assets
               
          for(let ast of Object.keys(finance.assets['Stocks'])){
              const asset:Stock = finance.assets['Stocks'][ast]
              let lastUpdateDate = asset.lastUpdateDate.seconds

              const stkPrice:any = await findStockPrice(asset.Name, asset["Share Count"])
              if(stkPrice !== null){
                finance.assets[astClass][ast].value = stkPrice
                finance.assets[astClass][ast].lastUpdateDate = Timestamp.now()
              }
          }
      });
   }
});

The third-party API call method is like the below:

async function findStockPrice(symbol:string, quantity:number){
    let value = null
    try {
      const url = 'https://someurl.com?' + symbol
      const  header = {
        ...
      }

      const response = await fetch(url, {headers: header})
      const json = await response.json()

      const rate = json["rate"]
      value = quantity*rate

    } catch (error:any) {
      logger.error(error);
    }

  return value
}