> For the complete documentation index, see [llms.txt](https://spire-docs.gitbook.io/spire/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://spire-docs.gitbook.io/spire/pylon/features.md).
# Features
### Benefits of Running a Based Appchain
A based appchain combines the advantages of **running an** **appchain** (such as customizability, scalability, and sovereignty) with the benefits of **deploying a smart contract** on its base layer (such as composability and simplicity).
More specifically:
* Scalability - Dynamically adjust gas limits to support high throughput and user demand.
* Stability - Avoid “noisy neighbor” issues with tx fee isolation and dedicated execution.
* Accessibility - Seamlessly tap into parent chain's existing liquidity and users.
* Profitability - Capture more value with customizable fee structures and token models.
* Sovereignty - Full control over infrastructure, fees, and brand identity.
* Simplicity - Minimal infra to setup and manage—e.g. no duplicative oracle deployments.
## Seamless DevEx
Pylon enables us to have seamlessly composable transactions across chains within a [Sync Zone](/spire/pylon/architecture-overview.md#sync-zones). These seamlessly composable transactions enable us to provide a developer experience unlike any other. Your application contracts can literally be written as if they were on the same chain you are deployed under.
### Synchronously Composable Transactions
In order to provide this experience Pylon runs a node for the settlement chain you are deployed to as well as the sequencing node for your appchain and any other appchains in your [Sync Zone](/spire/pylon/architecture-overview.md#sync-zones). Pylon then detects whenever there is a transaction calling into another chain through a [Port Contract](/spire/pylon/architecture-overview.md#port-contracts). It forwards the call to the other chain and then injects the results back into the originating [Port Contract](/spire/pylon/architecture-overview.md#port-contracts) with a [Priming Transaction](/spire/pylon/architecture-overview.md#priming-transactions) that "frontruns" the original application call to ensure the data is available to complete the call.
[Forwarding Proxy Contracts](/spire/pylon/architecture-overview.md#forwarding-proxy-contracts) are used to take app calls and re-direct them to the [Port Contract](/spire/pylon/architecture-overview.md#port-contracts) that will have the call results available for retrieval (since the [Port Contract](/spire/pylon/architecture-overview.md#port-contracts) is pre-populated with the necessary data as indicated above).
As a result, your app logic can be written as if it were on the same chain as the contracts you are attempting to call into:
See [Example Cross-chain Transaction](/spire/pylon/architecture-overview.md#example-cross-chain-transaction) to see how Pylon makes this work!
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