SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e24d7b3d67f427412f57e17ea97fe59cb990041b406959480c77ac91328158a' 
  AND token = 'fZkOkTnr0iS0gbSZwcTtsTutrA38aOvjGuQorqR4Xg4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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