[Lyrapower]

Description

Closes #480

GET /api/v1/admin/users no longer issues per-user queries — the correlated subqueries were replaced by grouped LEFT JOIN aggregates in #256 (97c848a). What remained was the other half of the problem described in this issue: each request still aggregated every row of transactions and trade_offers, so latency and DB load kept growing with total platform activity even though only one page of users is returned.

Change

server/src/routes/admin.ts — the page of users is selected first in a page_users CTE, and both aggregates are restricted to that page with a batched IN (SELECT id FROM page_users):

• balance: transactions WHERE user_id IN (page) — uses the index on transactions(user_id) (migration 010)
• trade count: trade_offers WHERE seller_id IN (page) UNION ALL buyer_id IN (page) — uses the seller/buyer indexes (migration 010)

Still exactly two queries per request (page + total count) regardless of page size. Response shape, ordering (created_at DESC), and pagination metadata are unchanged.

Verification

Equivalence and performance on real Postgres 16 (20k users, ~500k transactions, ~100k trade offers, with the migration-010 indexes): old and new queries return byte-identical results for pages (limit, offset) = (20,0), (20,20), (50,0), (1,0), (7,13), (50,1000), (100,19950) and an out-of-range page. EXPLAIN ANALYZE for a 20-user page: 312.7 ms → 7.9 ms.

Tests (server/src/routes/admin.test.ts, new describe block):

• query count is identical for a 1-user page and a 50-user page (auth 2 + page 1 + count 1 = 4); any unexpected/per-user query fails the test
• empty page returns the same query count and correct pagination
• response keys and pagination metadata (page, limit, total, totalPages) unchanged; users with no activity still get 0
• the page query passes [limit, offset] and scopes both aggregates to page_users
• mutation check: with the previous SQL restored, the 4 new tests fail; with this change, all 24 tests in the file pass

Note on CI

main currently fails tsc --noEmit because of src/services/notifications.ts / src/__tests__/notificationTemplates.test.ts (missing renderTemplate export, undefined event/payload/renderTradeDisputeOpened). That breaks compilation of admin.test.ts under ts-jest on main too, so I ran the admin suite with ts-jest diagnostics turned off. This PR adds no new type errors (tsc --noEmit errors are all in those two notification files).

Disclosure: I use AI assistance. I ran the tests and reviewed every change before submitting.

[Lyrapower]

Hi! Sorry for the timing — this PR went up a few hours after Wave 10 closed. The work was ready, but my build environment was down overnight and I missed the cutoff. Would you be open to rolling #480 over to the next Wave? Happy to address any review feedback in the meantime.