SELECT 
  COUNT(*) 
FROM 
  cscart_countries 
WHERE 
  code = 'US' 
  AND status = 'A'

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_countries",
          "access_type": "const",
          "possible_keys": ["PRIMARY", "status"],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["code"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}