Most traditional or monolithic content management systems are “coupled,” meaning that the content management application (CMA) and the content delivery application (CDA) come together in a single application, making back-end user tools, content editing and taxonomy, website design, and templates inseparable. Coupled systems are useful for blogs and basic websites as everything can be managed in one place. However, in a coupled CMS, CMS code is tightly connected to any custom code and templates, which means developers have to spend more time on installations, customizations, upgrades, hotfixes, etc. and they cannot easily move their code to another CMS.
There is a lot of confusion around the differences between a decoupled CMS and a headless one because they have a lot in common; a headless CMS is a type of decoupled architecture. Like a headless CMS, a decoupled CMS separates the CMA and CDA environments, typically with content being created behind the firewall and then being synchronized and pushed to the delivery environment. The main difference between a decoupled CMS and a headless CMS is that the decoupled architecture is active—it prepares content for presentation and then pushes into the delivery environment—whereas a headless CMS is reactive—it sits idly until a request is sent for content.
Decoupled architecture allows for easier scalability and provides better security than coupled architecture, but it does not provide the same support for omnichannel delivery. Plus, there are multiple environments to manage, hiking up infrastructure and maintenance costs