Whether nginx shared dict 'lpop' command delete the key of list or not?

Openresty version: 1.13.6.2

According to our business needs, we need to create a list in nginx shared dict every second and put some elements into it, then there is a timer thread in nginx consumes the elements in the list with "lpop" command.
In our test environment, after "lpop" all the elements in the list, the key of the list will be "disappeared" automatically. But in our product environment, the key is still there even though the value of the list is empty. Since we will create a list in shared dict every second, it results in OOM in the specific shared dict.
We don't find any conclusions about the behavior of key of list data structure in shared dict in openresty official website. Does anyone know why this happened?

Start by reproducing the shared-dict list behavior described for OpenResty 1.13.6.2, focusing on the lpop command after the list becomes empty. Compare the test and product environments and inspect the shared-dict lpop entry point or documentation. Done means the key-retention behavior and resulting memory use are explained, documented, or corrected.