Triggering lambda on s3 upload

I upload many files using aws s3 sync command

Works perfectly and all files are uploaded. Then I have a trigger for a lambda that checks if all the files are uploaded and then I want to invoke another function

The problem is that if the files are uploaded very fast the lambda executes many times in concurrency!!

const s3Files = await s3.listObjectsV2(params).promise();

        const s3FileNames = [];
        s3Files.Contents.forEach((content) => {
            s3FileNames.push(content.Key);
        });

        // hidden code validating if file names are fine
        if(allLoaded) {
           //invoke another function
        } else { return; }

If I upload 10 small files, it executes invoke another function 10 times!! I only want to run ONCE.

Where do I save like a boolean saying if all loaded don't call the function again