SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c293d7b55bca94e581a21016770b83b53521ba52d098f5ee6421aafdf912eb75' 
  AND token = 'D9gN4GWoYox9v8KsFd0DgGD1lDoJt1tlIbxKURSIjhE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}