100x faster Postgres performance by changing 1 line

SELECT c.key,
c.x_key,
c.tags,
x.name
FROM context c
JOIN x
ON c.x_key = x.key
WHERE c.key = ANY (VALUES (15368196), — 11,000 other keys –)
AND c.x_key = 1
AND c.tags @> ARRAY[Eblah];