SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8250eefa1844c333cbb8849cbbabe9f6497b1d24299fb6725406efe0c53446d' 
  AND token = 'QFW+7h05fbxWfGykXNjvDlximTTIlJwVLajDgPDlccc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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