Techniques are provided for scheduled and non-scheduled delivery of messages. A message directed to at least one consumer is received at a message entity. The message is determined to include a scheduled delivery time. The received message is stored in a scheduled sub-queue of the message entity. Activation metadata is retrieved and stored for any messages stored in the scheduled sub-queue that include a scheduled delivery time within a predetermined upcoming time period. If when the message is received, the scheduled delivery time of the message is within a current activation window, the activation metadata for the message may be extracted and stored immediately. The stored activation metadata is analyzed to determine a batch of messages in the scheduled sub-queue ready for delivery. The determined batch of messages is stored in an active sub-queue of the message entity, to be ready for delivery at the request of a consumer.