Tightly-coupled

Tight coupling describes systems or components that are highly interdependent. Changes in one part of the system often necessitate changes in others. This contrasts with loose coupling, where components are designed to function relatively independently, reducing the ripple effect of modifications. In tightly-coupled architectures, modules share extensive information and have strong dependencies, frequently sharing state or internal data structures directly. While offering potentially higher performance in specific scenarios, tightly-coupled systems can be harder to modify, test, and scale due to their interwoven nature. Consequently, it demands precise planning and is susceptible to cascading failures if one component malfunctions.

Tightly-coupled meaning with examples

• The legacy mainframe system was a prime example of a tightly-coupled architecture. Every module relied heavily on the others, making even minor updates a monumental undertaking. Adding a new feature required coordinated changes across multiple interdependent components, increasing the risk of errors and extended downtime for system maintenance.
• In the early stages of the project, the developers created tightly-coupled modules that directly accessed shared memory. The design initially accelerated development; however, it later created many problems. This design hindered unit testing and made debugging complex as any modification caused widespread side effects across the application.
• When the database schema was altered in the old system, the change initiated an error cascade. Since the application layers were tightly coupled, the database change broke multiple functions across several sections. Fixing this required an expensive, time-consuming effort to reconcile all the affected modules with the schema updates.
• The team discovered that their microservices were unintentionally becoming tightly-coupled through the frequent use of synchronous calls and direct data sharing. This realization prompted them to refactor their code to adopt more asynchronous communication to increase the maintainability of their system, and improve scalability.
• The initial design of the robot's control system was flawed, employing tightly-coupled sensor and actuator interactions. The design led to a cascading failure when one sensor malfunctioned. Redesign was required to implement a more loosely-coupled system that could function regardless of isolated sensor failure.