Throughout 2022 by 2023 we noticed plenty of progress being made in scaling Ethereum by way of layer 2 networks. Optimistic-based rollups equivalent to Arbitrum and Optimism had been joined by rollups utilising zero-knowledge know-how utilized by Polygon ZK-EVM, Linea, ZK-Sync, Scroll, Starknet and others. The entire suppliers of layer 2 networks are conscious that scaling blockchain networks does not finish with layer 2, there’s a further layer to the stack — layer 3 or appchains which many contemplate the scalability nirvana for blockchains.
Appchains or application-specific blockchains provide better velocity, decrease transaction prices and are customised to serve specific use circumstances, not like public layer 2 blockchain networks.
Most of the groups who’ve launched layer 2 networks have not too long ago introduced devoted stacks for constructing appchains that sit on prime of their layer 2 networks.
The appchain stacks
On the time of writing, the entire following appchain stacks have been introduced by the foremost layer 2 groups:
Linea and Scroll are absent from this listing, however that is seemingly because of them having launched their layer 2 mainnets later than the opposite groups.
Exterior of the Ethereum ecosystem, you’ve appchain toolchains for a lot of different blockchain networks together with Polkadot (Substrate), Avalanche (Subnets) and Cosmos (Zones). These all provide EVM assist too to piggyback off the Ethereum ecosystem.
Rollups as a Service (RaaS)
Along with the groups constructing these appchain stacks, you’ve firms who historically provided blockchain as a service (BaaS) deployments extending their provides to incorporate rollups as a service (RaaS). The phrases rollup, appchain and layer 3 networks are getting used considerably interchangeably when referring to a lot of these networks. Additionally, Appchains as a Service is unlikely to catch on given its acronym… 🤔).
Non-public blockchain 2.0
In some respects, this seems like historical past repeating itself. 5 years in the past when BaaS choices had been first being provided, firms had been launching personal blockchain initiatives left, proper and centre.
It wasn’t simply the overhead of working personal networks, many initiatives merely did not warrant shifting past a proof of idea.
Organisations which can be investing now in web3 initiatives are wiser than they as soon as had been. They perceive the area and plenty of of them now recognise the attain that’s accessible by way of public networks.

They nonetheless face challenges on public networks, equivalent to the actual fact they’re competing with all different customers of the community and that transaction prices could also be greater than they like.
The attraction of appchains
Launching a devoted appchain might be interesting to them for these causes and others.
By launching an appchain, they’re able to management sure elements of the community, however inherit safety supplied by a layer 2 community with out having to bootstrap the belief themselves.
Which means the creator can specify the community configuration that most closely fits their use case. A few of the choices embody:
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The cryptocurrency or token used to pay for transactions on the community. Whether or not it is the forex of the underlying community equivalent to Ether, or the community’s personal token. They could even select a gasless community
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The block measurement. If the community goes to be processing giant volumes of easy transactions, a smaller block measurement might be used to extend throughput. Conversely, if transactions are extra complicated, a bigger block measurement might be specified.
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Restrictions on what wallets can transact with the community equivalent to solely people who have gone by a KYC course of.
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The frequency with which transaction or proof attestations are rolled up onto the underlying community it’s utilizing.
Moreover, the lifetime with which rollups are required varies. Not like blockchains, rollups could be ephemeral or momentary.
Ephemeral chains
The blockchain-heavy exercise can happen on a devoted rollup, which as soon as full, the rollup could be retired, with all state modifications maintained on the bottom community.
When somebody needs to subsequently append to this rollup state, equivalent to transferring possession of a minted NFT. They’ll undertake this operation on the community utilized by the rollup, as a full historical past of the ephemeral rollup is ceaselessly saved on the community it was secured by.
What number of appchains do you want?
With the entire exercise by layer 2 groups in launching their appchain stacks and blockchain infrastructure suppliers scrambling to assist them, we’ll see increasingly appchains being launched over the approaching months.
The query that’s on many individuals’s minds is how large the house is more likely to develop. Opinions range vastly, with some viewing there being a way forward for solely a whole lot of appchains, whereas others, a whole lot of hundreds of them.
It is useful for the bigger quantity to return to fruition for the sake of layer 2 groups and infrastructure suppliers, however not all traders are as satisfied of this at current.
Till we now have the subsequent wave of progress in web3, being pushed by new units of issues being solved by this know-how, we do not understand how large a component appchains will play on this. It is also seemingly that there shall be consolidation within the variety of appchain platforms as winners begin to emerge.
Common settlement layers
Appchains are an important piece of plumbing in serving to blockchains to scale. They transfer the execution of decentralised purposes onto their very own devoted networks to raised serve their wants, quite than overloading the underlying blockchain community.
This permits base layer networks equivalent to Ethereum to transition towards being common settlement layers, which given their decrease throughput and better prices is a way more applicable position for them to play for web3.
Many new appchains will launch over the approaching months. Not like standalone blockchain networks, they exist as a part of a broader ecosystem as they settle transactions on an underlying community.
These ecosystems will strengthen the propositions of lots of them. Nonetheless, it’s nonetheless going to take time for this panorama to ascertain itself and the true winners to emerge. Particularly when there are such a lot of layer 2 networks to select from and a necessity for better product-market slot in web3.