Distributed systems involve multiple computers or devices communicating over a network to accomplish tasks together. Common challenges include handling unreachable APIs, service downtime, authorization rejections, data format changes, and timeouts under heavy load. Modern applications often use distributed systems concepts such as Load Balancing, Command and Query Responsibility Segregation (CQRS), Two-Phase Commit, and Saga patterns. Developers working with these systems are effectively distributed systems developers, and tools like Temporal can help manage many of the associated challenges.