I started a series on X (formerly Twitter) where I post a LayerZero (LZ) “Word of the Week” and…

I started a series on X (formerly Twitter) where I post a LayerZero (LZ) “Word of the Week” and break it down into simpler terms for better understanding. In this series, I explain key terminologies related to LayerZero. So far, I’ve posted about nine articles on LZ concepts, and I’ve decided to start sharing them here on Medium as well.

For now, I’ll be transferring my weekly LZ Word of the Week posts here on Medium daily, so my Medium and Twitter stay in sync.

For today I’ll write about an interesting concept called Compose

In this post, we’ll cover → What is Compose? → Vertical composability → Horizontal composability → Conclusion

Enjoy 🥂

What is Compose?

Compose is simply the ability for smart contracts to work together like Lego blocks.

This is the ability to combine multiple cross-chain operations into a single transaction. Composition allows for complex cross-chain interactions while maintaining transaction integrity across multiple chains.

LZ compose or Composition is divided into two

→Vertical composability(for LayerZero V1)

→Horizontal composability(For layerZero V2)

Vertical composability

Vertical composability is the ability to stack multiple function calls inside a single transaction.

It works on the principle of “all or nothing.” This means if one function call fails, the entire transaction fails and no funds are lost.

So, it either goes through completely or it doesn’t go through at all.

Think of it like a bank transfer. For money to reach your friend: → You need to be debited by the bank. → Your friend needs to be credited. → A proof of the transaction must be recorded in the ledger.

If any of these steps fail, the whole transaction fails and your money is returned. That’s exactly how vertical composability works.

Horizontal composability

Horizontal composability lets multiple apps or contracts run independently.

If App A fails, App B can still execute its part on-chain.

Think of Horizontal compossibility like you are taking multiple exams. You pass Math, Chemistry, and Biology, but fail Physics. That doesn’t mean you’ve failed everything. You can always retake Physics later.

That’s how horizontal composability works , if one app fails, the rest continues, and you can retry the failed part without losing everything.

Conclusion

Finally even with horizontal compossibility transactions can still fail on the destination chain for various reasons(e.g insufficient gas ,contract logic and so on) LZ compose achieves guaranteed finality which means that your app is designed so that if a transaction is accepted on the source chain it will be accepted on the destination chain. Or if it cannot be accepted, the state remains consistent & "no state damage" occurs

Imo, horizontal composability is better for cross-chain swaps and bridging.

As more institutions launch their own chains, the demand to move value across chains will only grow.

This makes horizontal composability a powerful upgrade from vertical composability.

Now, my question to you: Which would you prefer vertical or horizontal composability?