use context.getRemainingTimeInMillis().js

module.exports.handler = (event, context, callback) => {
  let position = event.position || 0;
  
  do {
    ... // process the tasks in small batches that can be completed in, say, less than 10s
    // when there's less than 10s left, stop
  } while (position < totalTaskCount && context.getRemainingTimeInMillis() > 10000);
    
  if (position < totalTaskCount) {
    let newEvent = Object.assign(event, { position });
    recurse(newEvent);
    callback(null, `to be continued from [${position}]`);
  } else {
    callback(null, "all done");
  }
};