SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b9701c17e74da1e3d7285bbd0a59f40ed082b14be74bc50d588ab175bf9d76' 
  AND token = '5GfCPkBxm6j5f7TdZrsYJgcUy0BY2FdZesF+eKuyUwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Impossible WHERE noticed after reading const tables