Why / Why Not
Previously, projects had to secure a slot through parachain auctions, locking up substantial DOTs for long periods. The process was resource-intensive and posed a gigantic barrier to entry. With the rollout of Agile Coretime , running a parachain has become increasingly more approachable. This adds more weight to the consideration of implementing a blockchain as a Polkadot parachain, contrary to a solochain.
Why should you run a parachain?
Obviously, if the goal is to serve certain aspects of the Polkadot ecosystem, implementing a parachain would be the first choice for the free interoperability with other networks in the ecosystem (thanks to XCM ).
Most blockchain projects would want to focus on building innovative features rather than reinventing the wheel with consensus mechanisms and network infrastructure. Polkadot’s parachain architecture lets you do exactly that - you can concentrate on developing your application’s core functionality while the relay chain handles the complex networking, security, and consensus. If that’s the case, the project can benefit with faster development cycles and quicker deployment of your blockchain application.
The asynchronous backing  updates further enhance scalability by allowing parachains to produce blocks more frequently and with higher capacity.
As a prime example, by being a parachain, Acala  can focus on its core mission of building a DeFi infrastructure while leveraging Polkadot’s shared security, interoperability, and scalability features.
Why shouldn’t you run a parachain?
Bittensor  is a great example of a project that might not be well-suited to being a Polkadot parachain. It is a decentralized, incentive-driven machine learning network built using Substrate. While it initially explored integration as a Polkadot parachain, it ultimately chose to operate as a standalone solochain. This decision was driven by several key factors that align with Bittensor’s unique architecture and objectives.
Bittensor employs a hybrid consensus algorithm known as Yuma Consensus, which combines elements of Proof-of-Stake and Proof-of-Work. This mechanism is specifically designed to validate probabilistic outputs, such as AI-generated data, which traditional consensus models are ill-equipped to handle. Integrating such a specialized consensus into the Polkadot Relay Chain would be challenging, as Polkadot’s consensus is optimized for deterministic state transitions. Operating as a solochain allows Bittensor to maintain and evolve its consensus mechanism independently.
Bittensor’s architecture relies heavily on off-chain computations performed by miners who run AI models. These models process and respond to queries without recording each interaction on-chain, enhancing scalability and efficiency. Such an operational model does not align well with the on-chain execution environment of Polkadot parachains, which are designed for deterministic and verifiable computations. By remaining a solochain, Bittensor preserves the flexibility to manage off-chain activities without the constraints of on-chain execution requirements.
Bittensor’s native token, TAO, serves as both an incentive for network participants and a means of governance. The network distributes approximately 7,200 TAO daily to miners and validators, amounting to significant annual emissions. This economic model is tailored to reward contributions to AI model development and validation. Integrating into Polkadot’s shared security model would require aligning with its staking and bonding mechanisms, potentially complicating Bittensor’s bespoke tokenomics.
Bittensor initially launched on the Polkadot parachain but transitioned to an independent blockchain in March 2023. This move was influenced by the desire for greater control over network parameters and the recognition that its specialized requirements were better served outside the parachain framework.