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SELECT 
  * 
FROM 
  cscart_vd_vendors_relationships 
WHERE 
  brand_id = 139

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_vd_vendors_relationships",
          "access_type": "ref",
          "possible_keys": ["brand_id"],
          "key": "brand_id",
          "key_length": "4",
          "used_key_parts": ["brand_id"],
          "ref": ["const"],
          "rows": 18,
          "filtered": 100
        }
      }
    ]
  }
}

Result

id	brand_id	feature_id	variant_id	lang_code
12405	139	661	2198	es
12404	139	649	1925	es
12403	139	648	1897	es
12402	139	654	2142	es
12401	139	654	2141	es
12400	139	654	2140	es
12399	139	654	2137	es
12398	139	647	1889	es
12397	139	662	2219	es
12396	139	662	2205	es
12395	139	660	2189	es
12394	139	660	2188	es
12393	139	658	2179	es
12392	139	652	2108	es
12391	139	652	2124	es
12390	139	652	2109	es
12389	139	652	2125	es
12388	139	646	1887	es
12387	139	653	2128	es