Design a Distributed Counter

Functional Requirements:

• The system should support incrementing and decrementing a distributed counter.
• The current value of the counter should be retrievable at any time.
• The counter should be accessible and updatable from multiple nodes/data centers.
• The system should handle concurrent updates correctly (no double counting or missing updates).

Non-Functional Requirements:

• High availability: The counter should be available even if some nodes fail.
• Scalability: The system should support a large number of concurrent reads and writes.
• Low latency: Read and write operations should complete quickly.
• Eventual consistency: The counter value may be slightly stale but should converge to the correct value across all nodes.
• Fault tolerance: The system should handle network partitions and node failures gracefully.