SELECT 
  destination_id, 
  rate_value, 
  rate_type 
FROM 
  ushop_tax_rates 
WHERE 
  tax_id = 6 
  AND destination_id = 0

Query time 0.00050

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "Impossible WHERE noticed after reading const tables"
  }
}