From 9bbc18a57d17f69dc2a8f5eb0c8950fc4cf84293 Mon Sep 17 00:00:00 2001
From: NayiemW <nayiem@qredit.io>
Date: Fri, 15 May 2026 11:26:45 +0200
Subject: [PATCH] api: estimate counts by default, cache /blockchain burn
 totals
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estimateTotalCount in defaults previously evaluated to false when
CORE_API_ESTIMATED_TOTAL_COUNT was unset, which routed every list
endpoint through a real COUNT(*) inside a REPEATABLE READ transaction
on the api connection. statement_timeout (3s) kills COUNT(*) on a
mainnet-sized blocks or transactions table; the catch returns
totalCount: 0 with an empty data array under a 200, so clients see
silently empty results. Flip the default to true and treat the env
var as an explicit opt-out (=false).

BlockchainController.index calls two unbounded SUMs over transactions
per request, each ~30s on mainnet. Under explorer polling these pile
up holding api connections (load average 8+ observed under load).
Cache the result in-process with a 10-minute TTL and a single-flight
background refresh — values only change on blocks carrying burned
fees or burn transactions, and the endpoint's main consumers are
dashboards where that staleness is fine.
---
 packages/api/src/controllers/blockchain.ts | 43 +++++++++++++++++++++-
 packages/api/src/defaults.ts               |  2 +-
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/packages/api/src/controllers/blockchain.ts b/packages/api/src/controllers/blockchain.ts
index 65a8b39b2..3aa39fd75 100644
--- a/packages/api/src/controllers/blockchain.ts
+++ b/packages/api/src/controllers/blockchain.ts
@@ -8,6 +8,28 @@ import { WalletSearchResource } from "../resources-new";
 import { WalletSearchService } from "../services";
 import { Controller } from "./controller";
 
+// Burn totals only change when a new block carrying burned fees or burn
+// transactions is forged, so recomputing them on every /blockchain request
+// is wasteful — both queries are unbounded SUMs over the transactions table
+// and take tens of seconds on a mature mainnet. Cache the result and refresh
+// lazily in the background; a stale-but-fresh-on-read pattern is fine for an
+// endpoint whose primary consumers are explorer dashboards.
+interface BurnCache {
+    fees: string;
+    transactions: string;
+    ts: number;
+    refreshing: Promise<void> | null;
+}
+
+const burnCache: BurnCache = {
+    fees: "0",
+    transactions: "0",
+    ts: 0,
+    refreshing: null,
+};
+
+const BURN_CACHE_TTL_MS = 10 * 60 * 1000;
+
 export class BlockchainController extends Controller {
     @Container.inject(Container.Identifiers.BlockHistoryService)
     @Container.tagged("connection", "api")
@@ -34,8 +56,25 @@ export class BlockchainController extends Controller {
     public async index(_: Hapi.Request, h: Hapi.ResponseToolkit) {
         const { data } = this.stateStore.getLastBlock();
 
-        const fees = Utils.BigNumber.make(await this.transactionRepository.getFeesBurned());
-        const transactions = Utils.BigNumber.make(await this.transactionRepository.getBurnTransactionTotal());
+        if (Date.now() - burnCache.ts > BURN_CACHE_TTL_MS && !burnCache.refreshing) {
+            const repo = this.transactionRepository;
+            burnCache.refreshing = (async () => {
+                try {
+                    const [feesRaw, txRaw] = await Promise.all([
+                        repo.getFeesBurned(),
+                        repo.getBurnTransactionTotal(),
+                    ]);
+                    burnCache.fees = String(feesRaw);
+                    burnCache.transactions = String(txRaw);
+                    burnCache.ts = Date.now();
+                } finally {
+                    burnCache.refreshing = null;
+                }
+            })();
+        }
+
+        const fees = Utils.BigNumber.make(burnCache.fees);
+        const transactions = Utils.BigNumber.make(burnCache.transactions);
         const total = fees.plus(transactions);
 
         return {
diff --git a/packages/api/src/defaults.ts b/packages/api/src/defaults.ts
index 31b2a7f07..5a2ce49f5 100644
--- a/packages/api/src/defaults.ts
+++ b/packages/api/src/defaults.ts
@@ -69,7 +69,7 @@ export const defaults = {
     },
     options: {
         basePath: "/api",
-        estimateTotalCount: !!process.env.CORE_API_ESTIMATED_TOTAL_COUNT,
+        estimateTotalCount: process.env.CORE_API_ESTIMATED_TOTAL_COUNT !== "false",
     },
     ws: {
         banSeconds: 10,