SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 734 
WHERE 
  cscart_products_categories.product_id IN (
    1127, 1132, 1136, 1137, 1138, 1143, 1144, 
    1145, 1146, 1129, 1154, 1135
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00049

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_products_categories ALL PRIMARY,pt 29 Using where; Using filesort
1 SIMPLE product_position_source eq_ref PRIMARY,pt PRIMARY 6 const,hobilifedt.cscart_products_categories.product_id 1
1 SIMPLE cscart_categories eq_ref PRIMARY,c_status,p_category_id PRIMARY 3 hobilifedt.cscart_products_categories.category_id 1 Using where

Result

product_id category_ids position
1127 734M 0
1129 734M 0
1132 734M 0
1135 734M 0
1136 734M 0
1137 734M 0
1138 734M 0
1143 734M 0
1144 734M 0
1145 734M 0
1146 734M 0
1154 734M 0