Reduce Database Connections

[stefangutica]

Reasoning

• PersistenceModule.forRoot() was previously imported across multiple feature modules, forcing TypeORM to repeatedly initialize separate MongoDB connection pools.
• This redundant initialization caused an unnecessary connection spike from 13 to 93 upon application startup (+80 redundant connections for a custom start config).
• Moving the initialization to the root module eliminates this overhead, resulting in a ~62.5% reduction in newly spawned connections (dropping from +80 down to +30 for a custom start config).
• This optimization lowers the total peak connection load on the database server by ~54% (from 93 down to 43 connections for a custom start config), preventing potential connection exhaustion.

Proposed Changes

• Removed .forRoot() imports from all individual feature modules to prevent multiple pool allocations.
• Registered PersistenceModule.forRoot() exclusively within the main root module where the application is bootstrapped (listen).
• Utilized the existing @Global() decorator on the module to seamlessly distribute database repositories and PersistenceService globally across the app without breaking dependencies.
• EXTRA: remove queue.worker.module.ts which is not used anywhere

How to test

• Boot up the application locally and monitor active connections via MongoDB Compass (Performance tab) or mongosh using db.serverStatus().connections.
• Verify the optimized footprint: connection count spike should drop significantly
• Test various feature module endpoints (e.g., NFT metadata, media, settings) to ensure that the global database providers and repositories resolve correctly without throwing dependency errors.

[github-actions]

k6 load testing comparison.
Base Commit Hash: 733e9b6
Target Commit Hash: 71234de

Metric	Base				Target				Diff
	Avg	Max	90	95	Avg	Max	90	95	Avg	Max	90	95
Nodes	48.68	627.56	58.66	61.69	40.43	205.44	51.33	53.56	-16.93% ✅	-67.26% ✅	-12.50% ✅	-13.17% ✅
Tokens	48.87	436.81	58.71	61.75	40.51	266.76	51.35	53.50	-17.11% ✅	-38.93% ✅	-12.54% ✅	-13.37% ✅
Pool	48.76	439.38	58.68	61.67	40.43	227.17	51.31	53.66	-17.08% ✅	-48.30% ✅	-12.55% ✅	-12.99% ✅
Transactions	59.48	800.68	59.90	64.09	50.73	2208.37	52.14	54.91	-14.71% ✅	+175.81% 🔴	-12.95% ✅	-14.32% ✅
Mex	48.51	439.33	58.65	61.61	40.45	227.22	51.31	53.69	-16.63% ✅	-48.28% ✅	-12.50% ✅	-12.85% ✅
Blocks	53.31	658.10	59.18	62.83	45.36	637.14	51.96	55.27	-14.92% ✅	-3.19% ✅	-12.20% ✅	-12.04% ✅
Accounts	52.07	828.44	59.15	62.49	41.61	1448.44	51.41	53.89	-20.09% ✅	+74.84% 🔴	-13.08% ✅	-13.76% ✅
Test Run Duration	60003.22				60002.48

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