Consider some data:

WITH
  sequences AS (
    SELECT 0 as primary_key, 0 AS key1, 1 AS key2, 3 AS value1, 4 AS value2 UNION ALL
    SELECT 0, 1, 0, 8, 5 UNION ALL
    SELECT 0, 1, 1, 1, 2 UNION ALL
    SELECT 1, 2, 1, 1, 1 UNION ALL
    SELECT 1, 2, 3, 4, 4
  ),
  agg AS (
  SELECT
    primary_key,
    key1,
    key2,
    ARRAY_AGG((SELECT AS STRUCT f.* EXCEPT (key1, key2))) AS agg
  FROM sequences AS f
  GROUP BY
    primary_key,
    key1,
    key2
)
SELECT
  a.primary_key,
  a.key1,
  a.key2,
  ANY_VALUE(TO_JSON_STRING((agg))) AS result
FROM
  agg AS a
GROUP BY
  a.primary_key,
  a.key1,
  a.key2

This gives me data in format of:

However for future faster retrieval; I would like to get data in format of:

Any pointer on how I can make this happen?