SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '504b5b7ff2d41efa5dffcc0900389193996335cd04d22b3ef59891012ce5cb74' 
  AND token = 'C19xUl38Jwx52Sj6rGZuRR8G+wx56HbDNp1bOCZwzbM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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