Are there a cloud service that was reliably schedule execute a job at exact time?

I was writing server with serverless model, currently aws lambda. And have a requirement to run a job on exact datetime

Currently now I was running a cron job with aws cloudwatch to execute my server every minute, find all tasks which has timestamp older than present then do those task. Which is both wasteful and sometimes make a delay or in advanced by one minute from the actual time it need (because cloudwatch has maximum frequency only one ping per one minute). Not a desirable approach

And the work is not the same everyday. It can be dynamic datetime by client to ping my server

I wish there should be some service that like a message queue but can actively call target URL on scheduling timestamp. Is there something like that? It could be any service outside aws if it can put a URL for request

Thank you very much

Other solutions seem promising but there are another solution I found

using step functions wait state

http://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-wait-state.html

I cannot use it in my region yet because my region is singapore and it cannot be used across region. Currently now I would try to see a dynamodb solution above

As of 2018 step function was generaly available and work as expected