Transfers/Transactions performance improvements

[stefangutica]

Reasoning

• processTransactions issued one Redis GET per transaction to resolve pending results, so a single page meant N sequential round trips.
• Transaction actions were computed one at a time, serializing every cache / data-api call behind the previous transaction.
• Both are independent per transaction, so all of this page-level work was serialized for no reason.

Proposed Changes

• Resolve pending results for the whole page with a single batched getMany call, keeping the existing 20-minute cutoff.
• Compute transaction actions in parallel batches of 25 (BatchUtils.splitArrayIntoChunks), preserving the per-transaction error handling so one failure cannot fail the page.
• Run the two independent stages concurrently, and build the recognizers list with a single atomic assignment so concurrent callers cannot observe a partial or duplicated list.

How to test

• npm run test:unit — new tests cover the action batching, the batched pending-results lookup and the per-transaction error isolation.
• Diff responses before/after on /transactions and /transfers (including withScResults, withOperations, withLogs, withUsername, withActionTransferValue) — the payload must be identical.
• Check that recent pending transactions still report pendingResults: true / status: pending, and that MEX transactions still return their mex action rather than a generic scCall.

[github-actions]

k6 load testing comparison.
Base Commit Hash: ba269ea
Target Commit Hash: 5752887

Metric	Base				Target				Diff
	Avg	Max	90	95	Avg	Max	90	95	Avg	Max	90	95
Mex	34.29	411.89	47.88	52.86	41.73	632.13	53.55	57.58	+21.69% 🔴	+53.47% 🔴	+11.86% 🔴	+8.93% 🔴
Transactions	64.45	14315.82	53.32	57.24	47.13	778.07	56.14	58.82	-26.87% ✅	-94.56% ✅	+5.29% 🔴	+2.77% 🔴
Blocks	41.16	639.76	50.88	54.78	50.02	924.28	56.04	58.72	+21.52% 🔴	+44.47% 🔴	+10.15% 🔴	+7.19% 🔴
Tokens	34.15	413.21	47.77	52.87	41.54	454.88	53.27	57.66	+21.62% 🔴	+10.08% 🔴	+11.52% 🔴	+9.07% 🔴
Pool	34.19	412.80	47.81	52.84	41.55	496.69	53.28	57.65	+21.54% 🔴	+20.32% 🔴	+11.43% 🔴	+9.10% 🔴
Nodes	59.78	13684.53	63.80	101.25	70.80	18514.48	58.03	64.46	+18.44% 🔴	+35.30% 🔴	-9.04% ✅	-36.34% ✅
Accounts	40.70	681.15	52.00	55.84	41.17	191.87	53.41	57.51	+1.14% 🔴	-71.83% ✅	+2.70% 🔴	+2.99% 🔴
Test Run Duration	60005.27				60002.10

Legend: Avg - Average Response Time, Max - Maximum Response Time, 90 - 90th Percentile, 95 - 95th Percentile
All times are in milliseconds.