The current Ethereum network only creates a new block every 12 to 14 seconds. The growing user base increasingly strains the network leading to rising transaction fees. Various new techniques have been created to alleviate this strain on the network. In this talk, we will compare two prominent strategies for scaling Ethereum: 1. Sidechains implement a separate blockchain with lower transaction costs allowing payments to be run separately from the main Ethereum network. 2. In contrast, Optimistic rollups sit on top of Ethereum and process bundles of transactions off-chain in a different environment.

1. Scaling Ethereum
Sidechains, ZK-Proofs,
and Optimistic Rollups
Anthony Campolo
QuickNode Developer Advocate

2. Problem
The Ethereum network
creates a new block
every 12 to 14 seconds

3. Vitalik Buterin
Scalability, Part 1: Building on Top (2014)

4. Joseph Poon, Thaddeus Dryja
Bitcoin Lightning Network (2015)

5. Joseph Poon, Vitalik Buterin
Plasma: Scalable Autonomous Smart Contracts (2017)
Plasma is a proposed framework for incentivized and enforced
execution of smart contracts, scalable to a significant amount of state
updates per second (potentially billions)…
…enabling the blockchain to be able to represent a significant amount
of decentralized financial applications worldwide.

6. I - Plasma
● Child chain and root chain communication/arbitration secured by fraud proofs
● Each child chain has its own mechanisms for validating blocks
● Particular fraud proofs can be built on different consensus algorithms
Joseph Poon, Vitalik Buterin
Plasma: Scalable Autonomous
Smart Contracts (2017)

7. I - Plasma Pros and Cons
Pros ✅
● Layer 2 operations enable lower fees and faster computation
● Reduces amount of necessary data processing on Layer 1
● Compatible with Layer 1 scaling solutions like sharding
Cons ❌
● Paper sketches a system more than an implementation, leading to
multiple implementations (Plasma MVP, Cash, and Debit)
● Funds can only be withdrawn after lengthy waiting period

8. II - Sidechains
● Separate Layer 2 chains operating independently and running in
parallel to Layer 1 (Ethereum Mainnet), connected by a two-way bridge.
● Has own consensus algorithm and block parameters.
Vaibhav Saini
Difference between SideChains
and State Channels (2018)

9. II - Sidechains Pros and Cons
Pros ✅
● Established technology
● Supports general computation
Cons ❌
● Less decentralized
● Separate consensus mechanism not secured by Layer 1
● Quorum of validators can commit fraud

10. II - Sidechain Implementation - Polygon
● Clone of Layer 1 chain that supports
transferring assets to and from Layer 1
to Layer 2.
● Layer 2 is a new blockchain with its own
consensus mechanism for creating
blocks.
Polygon Lightpaper (2021)

11. III - ZK-Rollups
● Layer 2 scaling solution in which all
funds are held by a smart contract on
the Layer 1 chain, while computation
and storage are performed off-chain.
● For every Rollup block, a state
transition zero-knowledge proof is
generated and verified by the Layer 1
chain contract.
● Mass transfer processing of
hundreds of transfers is rolled into a
single transaction
Xavier Salleras, Vanesa Daza
Zero-Knowledge Proofs in
Embedded Systems (2021)

12. III - ZK-Rollups Pros and Cons
Pros ✅
● Reduced fees per user transfer
● Less data contained in each transaction
● Does not require a fraud game verification
Cons ❌
● Computing zero knowledge proofs requires data optimization for
maximum throughput
● Security scheme assumes a level of unverifiable trust

13. IV - Optimistic Rollups
● ZK-Rollups prove to Ethereum that transactions are valid
● In contrast, Optimistic Rollups assume the transactions are valid and
leave room for others to prove fraud.
Sam Richards, Corwin Smith
Optimistic Rollups (2022)

14. IV - Optimistic Rollups Pros and Cons
Pros ✅
● EVM and Solidity compatible
● More flexible than ZK-Rollups
● Data is available and secured on-chain
Cons ❌
● Limited throughput compared to ZK Rollups
● Requires both an honest majority of Ethereum validators and at
least one aggregator that does not censor transactions

15. IV - Optimistic Rollup Implementation #1 - Arbitrum
● Alice and Bob will engage in a back-
and-forth protocol, refereed by an L1
contract, to resolve their dispute with
minimal work required from any L1
contract.
● Arbitrum's approach is based on
dissection of the dispute.
Arbitrum White Paper (2018)

16. IV - Optimistic Rollup Implementation #2 - Optimism
● State commitments published to Layer 1
without direct proof of commitment
validity. Considered pending for a period
of time, a "challenge window”.
● If proposed state commitment goes
unchallenged for duration of challenge
window (7 days), it’s considered final.
● Once commitment considered final,
Layer 1 smart contracts safely accept
proofs based on commitment. Paradigm Research
How does Optimism’s
Rollup work? (2021)

17. Citations
Scalability (2014), V. Buterin
blog.ethereum.org/2014/09/17/scalability-part-1-building-top/
Bitcoin Lightning Network (2015), J. Poon, T. Dryja
lightning.network/lightning-network-paper.pdf
Plasma (2017), J. Poon, V. Buterin
plasma.io/plasma.pdf
Sidechains and State Channels (2018), V. Saini
hackernoon.com/difference-between-sidechains-and-state-
channels-2f5dfbd10707
Polygon (2021)
polygon.technology/lightpaper-polygon.pdf
ZK Proofs in Embedded Systems (2021), X. Salleras, V. Daza
eprint.iacr.org/2021/1382
Optimistic Rollups (2022), S. Richards, C. Smith
ethereum.org/en/developers/docs/scaling/optimistic-rollups/
Arbitrum (2018)
usenix.org/system/files/conference/usenixsecurity18/sec18-
kalodner.pdf
How does Optimism’s Rollup work? (2021), Paradigm Research
research.paradigm.xyz/optimism

18. QuickNode
Home Page quicknode.com
Twitter twitter.com/QuickNode
Events lu.ma/QuickNode
Apr 25 7:30 lu.ma/qnxbuildspace
Jobs jobs.lever.co/quicknode
Discord discord.gg/f2jmEtmSWY

19. Slides
https://www.slideshare.net/
AnthonyCampolo/eth-amsterdam-
scaling-ethereum/