The image adque_usershard1 illustrates user sharding using four keys: two red, two green, two blue, and two pink. Enqueue Transaction 1 has one of each red, green, blue and pink keys enqueued. Enqueue Transaction 2 has another set of each of red, green, blue and pink keys enqueued. Both transactions perform enqueues in parallel. Shard A stores the red and blue messages. Shard B stores the green and pink messages. Shard A and Shard B has one active dequeue session each.