SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df33a263118f05b00bef3fa4d9efe737ba27b9162dc952d382027af2990aea7f' 
  AND token = 'eJE4hzqvc7PPv3BijfVG41ywyntjZ+LQK0pkCI1s8j8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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