Loose coupling is one of the essential primary characteristics of SOA, and it can be easily achieved by having event-driven and messaging as part of a service's design. The services that we design should represent a business function or domain and consider an application that needs to send an email to the user immediately after booking a hotel and assume we have a hotel booking service that can book a hotel and send a confirmation email to the user. As per the business functions, we can have two different services; one that takes care of the hotel booking, and another one that takes care of the post-booking process such as email, mobile confirmations, and so on. The email service can receive events from the booking service, or it can listen for any messages from other systems, depending on its event-driven design or message-driven design.