Lesson Objective
Understand Blockchain Architecture Selection
In the previous lesson, you followed the technical lifecycle of a blockchain transaction[cite: 8]. This lesson now asks a deeper architectural question: should the blockchain be public, private or shared between selected organisations?[cite: 8] By the end of this lesson, you will be able to compare blockchain types using permission models, validator control, transparency, governance, privacy and performance requirements[cite: 8].
Audio Lesson
Listen to This Lesson
The audio version provides a comprehensive architectural comparison, exploring the trade-offs between permissionless public networks, controlled private enterprise frameworks, and multi-party consortium governance agreements[cite: 8].
Architecture Overview
The Type of Blockchain Changes the System
A blockchain is not automatically public, private, decentralised or suitable for every use case[cite: 8]. The architecture depends on who can join the network, who can validate transactions, who can read data, who controls upgrades and how quickly the system needs to process activity[cite: 8]. Public blockchains move trust towards open protocols and decentralised validators[cite: 8]. Private blockchains move control towards an organisation[cite: 8]. Consortium blockchains distribute control between a selected group of trusted organisations[cite: 8].
Selection Algorithm
Public vs Private Blockchain Selection
| Step | Process | Technical Selection Meaning |
|---|---|---|
| Step 1 | Understand public blockchains | Assess whether the system requires permissionless access, open validators and public auditability[cite: 8]. |
| Step 2 | Understand private blockchains | Assess whether the system requires permissioned identities, known validators and organisational control[cite: 8]. |
| Step 3 | Understand consortium blockchains | Assess whether several trusted organisations need shared validation and joint governance[cite: 8]. |
| Step 4 | Compare transparency | Decide whether ledger data should be public, restricted, encrypted or visible only to approved members[cite: 8]. |
| Step 5 | Compare governance | Identify who controls validators, permissions, protocol rules, upgrades and dispute resolution[cite: 8]. |
| Step 6 | Compare privacy | Decide whether data should be stored publicly, encrypted, permissioned or kept off-chain with hashes on-chain[cite: 8]. |
| Step 7 | Compare performance | Evaluate throughput, validator count, latency, cost, scalability and consensus overhead[cite: 8]. |
| Step 8 | Choose the correct blockchain type | Select the architecture that matches the technical and organisational requirements[cite: 8]. |
Step 1
Understand Public Blockchains
A public blockchain is permissionless[cite: 8]. This means anyone can create a wallet, submit transactions, inspect ledger activity and, depending on the protocol, participate in validation[cite: 8]. Trust is not placed in one company or central administrator[cite: 8]. Instead, trust is distributed across the network through cryptography, consensus rules and economic incentives[cite: 8]. Public chains are useful when openness, independent verification and censorship resistance are more important than privacy or centralised performance control[cite: 8].
Technical Point
Public blockchains use permissionless access, open validation and transparent ledger inspection to reduce reliance on central authorities[cite: 8].
Step 2
Understand Private Blockchains
A private blockchain is permissioned[cite: 8]. Users, applications and validator nodes must be approved before they can interact with the network[cite: 8]. This architecture is common in enterprise settings where identity, compliance, confidentiality and administrative control matter[cite: 8]. A private blockchain may still use blocks, hashes, signatures and validation rules, but the validator set is usually smaller and known[cite: 8]. This can reduce consensus overhead and improve speed, but it also makes the system less decentralised than a public blockchain[cite: 8].
Technical Point
Private blockchains combine blockchain-style records with controlled identity, known validators and organisational governance[cite: 8].
Step 3
Understand Consortium Blockchains
A consortium blockchain is governed by several approved organisations rather than one owner or a fully open public network[cite: 8]. Each member may operate a validator node, participate in governance decisions and share responsibility for maintaining the ledger[cite: 8]. This model is useful for banking networks, supply chains, logistics, healthcare partnerships, government systems and industry groups where multiple organisations need shared verification without exposing everything to the public[cite: 8].
Technical Point
Consortium blockchains are permissioned networks where governance and validation are distributed across selected organisations[cite: 8].
Step 4
Compare Transparency
Transparency determines who can inspect the ledger[cite: 8]. In a public blockchain, transaction metadata and ledger history are usually visible to everyone, even if wallet identities are pseudonymous[cite: 8]. In a private blockchain, visibility can be restricted to internal users, departments or authorised applications[cite: 8]. In a consortium blockchain, approved members may share ledger visibility while hiding sensitive commercial details from external parties[cite: 8].
Technical Point
Transparency controls who can read, inspect and verify blockchain activity[cite: 8].
Step 5
Compare Governance
Governance defines who controls the blockchain over time[cite: 8]. This includes who can approve validators, change protocol rules, modify access permissions, upgrade smart contracts, resolve disputes and respond to security incidents[cite: 8]. Public chains usually depend on community governance, protocol developers and validator incentives[cite: 8]. Private chains centralise governance in one organisation[cite: 8]. Consortium chains use shared governance agreements between approved members[cite: 8].
Technical Point
Governance controls the human and organisational rules behind the technical blockchain protocol[cite: 8].
Step 6
Compare Privacy
Privacy is one of the strongest reasons to choose a private or consortium blockchain[cite: 8]. Public chains expose transaction metadata by design, even when users are represented by wallet addresses rather than real names[cite: 8]. Enterprise systems may need encrypted payloads, role-based access, permissioned reads or off-chain storage where only a hash is placed on-chain[cite: 8]. This allows the blockchain to verify integrity without exposing the full sensitive record[cite: 8].
Technical Point
Privacy design decides whether sensitive data is public, encrypted, permissioned or represented by verification hashes[cite: 8].
Step 7
Compare Performance
Performance is not only about speed[cite: 8]. It includes transaction throughput, latency, validator count, consensus complexity, storage cost and network overhead[cite: 8]. Public blockchains may have lower throughput because many independent nodes must agree under open network conditions[cite: 8]. Private and consortium blockchains can often process transactions faster because they use known validators, controlled membership and lighter permissioned consensus[cite: 8].
Technical Point
Performance depends on validator count, consensus overhead, network openness and how much decentralisation the system requires[cite: 8].
Step 8
Choose the Correct Blockchain Type
Blockchain selection should be based on requirements, not hype[cite: 8]. A public blockchain is appropriate when the system needs open participation, decentralised trust and public auditability[cite: 8]. A private blockchain is appropriate when one organisation needs controlled access, known validators and data confidentiality[cite: 8]. A consortium blockchain is appropriate when several organisations need to share verification, governance and trust without making the system fully public[cite: 8].
Technical Point
Good blockchain design begins with requirements: openness, control, shared governance, privacy and performance[cite: 8].
Key Takeaways
What You Should Remember
Public Blockchain
Permissionless, transparent and decentralised, but usually slower and less private[cite: 8].
Private Blockchain
Permissioned, controlled and privacy-focused, but less decentralised[cite: 8].
Consortium Blockchain
Shared between approved organisations with joint validation and governance[cite: 8].
Architecture Selection
The correct choice depends on access, validator control, transparency, privacy and performance[cite: 8].
Knowledge Check
Quick Public vs Private Blockchain Quiz
Test your understanding. The questions can change when you refresh them[cite: 8].
Lesson Summary
Public, Private and Consortium Blockchains
Public blockchains are open, permissionless systems designed for public auditability and decentralised trust[cite: 8]. Private blockchains are permissioned systems designed for organisational control, known validators and stronger privacy[cite: 8]. Consortium blockchains sit between these models by allowing several approved organisations to share validation and governance[cite: 8]. The best architecture depends on the system’s requirements, including access, transparency, governance, privacy, validator control and performance[cite: 8].