25   struct Node {  struct
26     Node() {}  in Node()  function
27     explicit Node(const uint64_t key, const std::string& val = std::string())  in Node()  argument
30     uint64_t key_ = 0;
31     std::string val_;
56   struct Node : LRUElement<Node> {  struct
57     Node() {}  in Node()  function
58     explicit Node(const uint64_t key, const std::string& val = std::string())  in Node()  argument
61     uint64_t key_ = 0;
62     std::string val_;
63     std::atomic<uint32_t> refs_{0};