littleshop/Hostinger/FAST_SYNC_OPTIMIZATION.md

Fast Sync Optimization for BTCPay Server

Date: September 16, 2025

Optimizations Applied

Bitcoin Core Fast Sync

• dbcache: Increased from 1000MB to 2000MB for faster processing
• assumevalid: Added recent block hash to skip signature verification for known-good blocks
  • Hash: 00000000000000000002a23d6df20eecec15b21d32c75833cce28f113de888b7
  • This significantly speeds up initial sync by skipping cryptographic verification

Monero Fast Sync

• fast-block-sync: Enabled for faster block processing
• block-sync-size: Set to 20 blocks per batch
• max-concurrency: Increased from 2 to 4 threads
• db-sync-mode: Changed from safe:sync to fast:async:250000000bytes
  • safe:sync - Slowest but safest (original setting)
  • fast:async - Much faster, slight risk if power loss during sync
  • fastest:async - Maximum speed but highest risk (not recommended)

Configuration File

Location: /opt/btcpayserver-docker/docker-compose.override.yml

version: "3.6"

services:
  bitcoind:
    environment:
      BITCOIN_EXTRA_ARGS: |
        prune=10000
        maxmempool=300
        dbcache=2000
        maxconnections=40
        rpcthreads=6
        assumevalid=00000000000000000002a23d6df20eecec15b21d32c75833cce28f113de888b7        

  monerod:
    environment:
      MONERO_EXTRA_ARGS: |
        --prune-blockchain
        --sync-pruned-blocks
        --fast-block-sync=1
        --block-sync-size=20
        --max-concurrency=4
        --db-sync-mode=fast:async:250000000bytes        

Expected Sync Times (With Optimizations)

Before Optimizations

• Bitcoin: 24-36 hours
• Monero: 48-72 hours

After Optimizations

• Bitcoin: 8-12 hours (from current 43% progress)
• Monero: 18-24 hours (from current 0.2% progress)

Alternative Fast Sync Options

1. Bootstrap Files (Not Used)

• Download pre-synced blockchain data
• Pros: Very fast (2-4 hours)
• Cons: Trust required, large download (50GB+)

2. Remote Node (Not Used)

• Connect to existing synced node
• Pros: Instant availability
• Cons: Less privacy, dependency on external service

3. Checkpoint Sync (Partially Used)

• Bitcoin: assumevalid implemented
• Monero: Built-in checkpoints used automatically

Monitoring Commands

Check Sync Progress

# Bitcoin
sudo docker exec btcpayserver_bitcoind bitcoin-cli getblockchaininfo | grep -E "blocks|progress"

# Monero
sudo docker exec btcpayserver_monerod monerod status

View Sync Speed

# Bitcoin (blocks per minute)
sudo docker logs btcpayserver_bitcoind --tail 100 | grep UpdateTip

# Monero (blocks per second)
sudo docker logs btcpayserver_monerod --tail 100 | grep Synced

Safety Notes

• fast:async mode trades some safety for speed
• After sync completes, mode automatically becomes safer
• Power loss during sync may require resync of recent blocks
• Pruning remains active to limit disk usage

Rollback if Needed

Backup saved at: /opt/btcpayserver-docker/docker-compose.override.yml.backup-*

sudo cp /opt/btcpayserver-docker/docker-compose.override.yml.backup-* /opt/btcpayserver-docker/docker-compose.override.yml
cd /opt/btcpayserver-docker
sudo docker-compose restart bitcoind monerod