SELECT 
  pf.feature_id 
FROM 
  cscart_product_variation_group_features AS gf 
  INNER JOIN cscart_product_filters AS pf ON gf.feature_id = pf.feature_id 
WHERE 
  pf.feature_id > 0 
  AND pf.filter_id IN (10) 
LIMIT 
  1

Query time 0.00231

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pf",
          "access_type": "const",
          "possible_keys": ["PRIMARY", "feature_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["filter_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "gf",
          "access_type": "ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["feature_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100,
          "using_index": true
        }
      }
    ]
  }
}