SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ad6446c4a6347518d6a9e05c7a0d5dc8c6f01143dd474145d55751c84bd487d' 
  AND token = '5twCbCliXgMz2h2ZwOuSbzRrPq8LhRuuTrpm1LuO9To=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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