feat: batch payout txs, background analytics, submissions pagination

[k-deejah]

Description

This PR implements three performance improvement issues targeting batch payouts, background analytics computation, and submissions pagination.

---

Linked Issues

• Closes Batch payout transactions where Stellar supports multi-operation transactions #1981 — Batch payout transactions
• Closes Move heavy analytics computation to background jobs #2004 — Move heavy analytics computation to background jobs
• Closes Add pagination limit clamp and default to submissions listing #1973 — Add pagination limit clamp and default to submissions listing

---

Changes Made

#1981 — Batch payout transactions

Problem: Individual payouts are submitted as separate transactions, incurring per-transaction fees and RPC round-trips.

Solution: Group eligible payouts into multi-operation Stellar transactions (up to 100 ops/tx).

• StellarService.sendBatchPayments() (src/modules/stellar/stellar.service.ts): Builds a single TransactionBuilder with multiple Operation.payment() calls, signs once, submits once. Splits into multiple transactions when input exceeds 100 operations.
• PayoutsService.processBatchPayouts() (src/modules/payouts/payouts.service.ts): Cron job (every 30s) that queries pending/retry payouts, groups by asset, delegates to sendBatchPayments(). Handles partial failures per-payout.
• Updated claimPayout to set status to PENDING so batch cron picks it up.
• Metrics: batch_payout_total, batch_payout_operations, batch_payout_size.

#2004 — Move analytics to background jobs

Problem: Synchronous analytics computation blocks request threads and risks timeouts.

Solution: Compute in background jobs, persist results, serve precomputed data.

• PlatformAnalyticsService.getPlatformStats() (src/modules/analytics/services/platform-analytics.service.ts): First attempts to serve from the most recent AnalyticsSnapshot (within 5 min). Falls back to live computation when no fresh snapshot exists.
• computeAndStorePlatformStats(): Computes full platform stats and persists to analytics_snapshots table via upsert.
• @Cron(EVERY_5_MINUTES) computePlatformAnalytics(): Scheduled background job that pre-computes stats for the last 30 days.
• Metrics: analytics_computation_total (source: snapshot|live), analytics_computation_duration_seconds.

#1973 — Pagination limit clamp for submissions

Problem: GET /quests/:questId/submissions accepted unbounded limits, returning all submissions.

Solution: Wired existing QuerySubmissionsDto to controller; cursor-based pagination with @Max(100) limit clamp.

• Controller (src/modules/submissions/submissions.controller.ts): Accepts @Query() query: QuerySubmissionsDto.
• Service findByQuest() (src/modules/submissions/submissions.service.ts): Cursor-based pagination with filters (status, userId), sort (sortBy, order), limit (default 10, max 100).
• Returns PaginatedResponseDto<Submission> with data, nextCursor, hasMore.

---

Type of Change

• New feature (non-breaking change that adds functionality)
• Refactor (no functional change)
• Bug fix
• Breaking change
• Security fix

---

Test Evidence

Unit Tests

• New tests added for batch payouts (groups by asset, 100-op limit, partial failure)
• New tests for sendBatchPayments (multi-op tx, >100 splits)
• All existing tests pass (npm run test)

Test output:

PASS src/modules/payouts/payouts.service.spec.ts
PASS src/modules/stellar/stellar.service.spec.ts
Tests:       17 passed, 17 total

TypeScript Compilation

npx tsc --noEmit — no new errors introduced

---

Performance Impact

Area	Before	After	Improvement
Payout tx submission	1 tx per payout	1 tx per 100 payouts	~100x fewer txs
Analytics endpoint	Synchronous heavy query	Serves from snapshot	~10-50x faster response
Submissions listing	Returns all rows	Cursor paginated (max 100)	Bounded response size

---

[drips-wave]

@k-deejah Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[RUKAYAT-CODER]

kindly resolve conflict

[RUKAYAT-CODER]

Thank you for contributing to the project.