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Design patterns help you solve common problems and keep your code maintainable, and extensible. The observer pattern is used when a change in an object should trigger changes in the observing objects. Using Transaction Logs to implement Observer Pattern is the most common way to implement this pattern in web apps. There are many ways this pattern can be implemented, such as using Web Framework’s Observers and using periodic jobs to trigger the observer code based on the type of events. Using a simple background job to scan through the database tables and based on changes the observers code is run synchronously or asynchronously.