Sharding

How sharding is implemented and used to scale in Quai Network.

Making Blockchains Work Like Modern Databases

Traditional databases solved the scaling problem decades ago through sharding - splitting data across multiple servers. Quai brings this proven approach to blockchain, but with a crucial innovation: maintaining full security across all shards.

What is Sharding?

Database Sharding (Traditional): Imagine a library that gets too big for one building:

• Solution: Split books across multiple buildings (shards)
• Benefit: More librarians can help visitors simultaneously
• Challenge: Need a system to know which building has which book

Blockchain Sharding: The same concept, but for decentralized networks:

• Traditional approach: Split both data AND security (dangerous)
• Quai’s approach: Split only data, keep security unified (safe)

How Quai Implements Sharding

Key Benefits:

1. Parallel Processing

   • Each shard processes transactions independently
   • Like having multiple checkout lines instead of one
   • Result: 50,000+ TPS capacity

2. Lower Node Requirements

   • Nodes can choose to track only specific shards
   • Reduces hardware requirements for participation
   • More accessible = more decentralized

3. Geographic Optimization

   • Shards naturally organize by region
   • Minimizes latency within each shard
   • Better performance worldwide

Smart Address System

The Problem: How do you know which shard handles which transaction?

Quai’s Solution: Addresses contain built-in routing information - like ZIP codes for blockchain.

How It Works: Every Quai address has a 9-bit prefix that acts like a postal code:

• First 4 bits: Region identifier (like country)
• Next 4 bits: Zone within region (like city)
• Last bit: Currency type (Quai or Qi)

Formatting

The table below specifies the format for each bit in the shard identifier.

bits 0-3	bits 4-7	bit 8
region number	zone number	ledger identifier

Simple Examples

Example Address (shortened)	Location	Currency
0x000…	Region 0, Zone 0	Quai
0x2A4…	Region 2, Zone 10	Quai
0x008…	Region 0, Zone 0	Qi

Benefits:

• Instant routing: Nodes immediately know where to send transactions
• No lookups needed: Address itself contains all routing info
• Efficient processing: Eliminates cross-shard confusion

For technical details, see QIP-2.

The Security Breakthrough

Traditional Sharding’s Fatal Flaw:

• 10 shards = each gets 1/10th of security
• Attackers can focus on the weakest shard
• Like having 10 weak locks instead of one strong lock

Quai’s Innovation: Through coincident blocks and merged mining:

• Every shard maintains 100% network security
• Attacking one shard requires attacking the entire network
• Like having the same unbreakable lock protecting every door

How It Works:

1. Hierarchical structure organizes all shards
2. Hash linked references connect every chain
3. Atomic operations ensure all shards advance together
4. Result: Unlimited shards, uncompromised security

Legacy Testnet Mappings

Early testnets use a lighter 9-shard hierarchy. It has already been concluded that the mainnet should accommodate more than 9 shards, so this mapping is no longer recommended. We make note of it here for wallet compatibility with early testnets.

To find the address shard specification in detail please visit QIP-4.