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Frequently Asked Questions (FAQs)

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This FAQ focuses on technical questions for users interested in developing applications for Polkadot. If you have a more general question, you may wish to search for the answer on our support Knowledge Base or the main Polkadot network FAQ. If you have a question that is not answered, please feel free to ask on the Polkadot Watercooler Element channel or contact Polkadot Support.

Polkadot Launch​

The Genesis block of the Polkadot network was launched on May 26, 2020 at 15:36:21 UTC, as a Proof of Authority (PoA) network, with governance controlled by the single Sudo (super-user) account. During this time, validators started joining the network and signaling their intention to participate in consensus.

The network evolved to become a Proof of Stake (PoS) network on June 18, 2020. With the chain secured by the decentralized community of validators, the Sudo module was removed on July 20, 2020, transitioning the governance of the chain into the hands of the token (DOT) holders. This is the point where Polkadot became decentralized.

The final step of the transition to full-functioning Polkadot was the enabling of transfer functionality, which occurred on Polkadot at block number 1_205_128 on August 18, 2020, at 16:39 UTC.

On August 21, 2020, Redenomination of DOT occurred. From this date, one DOT (old) equals 100 new DOT.

Polkadot Roadmap​

For more information on the Polkadot roadmap please visit the official Polkadot website.

Consensus​

Why do we need Consensus?​

Consensus is a method for coming to agreement over a shared state. In order for the state of the blockchain to continue to build and move forward, all nodes in the network must agree and come to consensus. It is the way that the nodes in a decentralized network are able to stay synced with each other. Without consensus for the decentralized network of nodes in a blockchain, there is no way to ensure that the state one node believes is true will be shared by the other nodes. Consensus aims to provide the objective view of the state amid participants who each have their own subjective views of the network. It is the process by which these nodes communicate and come to agreement, and are able to build new blocks.

What are PoW and PoS?​

Proof of Work (PoW) and Proof of Stake (PoS) have been inaccurately used as short hand to refer to consensus mechanisms of blockchains, but that does not capture the full picture. PoW is the method for agreeing on a block author and part of the fuller Nakamoto consensus that also encompasses a chain selection algorithm (longest chain rule in Bitcoin). Similarly, PoS is a set of rules for selecting the validator set and does not specify a chain selection rule or how a chain might reach finality. PoS algorithms have traditionally been paired with an algorithm for coming to Byzantine agreement between nodes. For example, Tendermint is a practical Byzantine fault tolerant algorithm that uses PoS as its validator set selection method.

Why not Proof of Work?​

Although simple and effective in coming to a decentralized consensus on the next block producer, proof of work with Nakamoto consensus consumes an incredible amount of energy, has no economic or provable finality, and has no effective strategy in resisting cartels.

Validators​

How do I apply to be a validator?​

There is no central authority that decides on validators, so there is not per se an application that you can fill out. Registering as a validator is permissionless; in order to become one you must only set up a validator node and mark your intention to validate on chain. For detailed instruction on how to do validate you can consult the validator guide.

However, once you've set up a validator and have registered your intention it does not mean that you will be included in the active set right away. The validators are elected to the active set based on the results of an election algorithm known as Phragmén's method. Phragmén's method tries to accomplish two goals: 1) select n members from a larger set based on stake-weighted votes and 2) equalize the stake backing each validator as much as possible.

You will likely want to campaign your validator to the community in order to get more backing. You are looking for nominators that will put up their tokens to increase the stake for your validator. For validators who cannot acquire the minimum stake from the community, Parity and Web3 Foundation also run a joint programme called Decentralized Nodes that will nominate validators if they apply and fit the requirements.

How are validators rewarded?​

Validators are rewarded from the inflation of the relay chain, transaction fees, and tips. However, they only take a percentage of the former two. More details can be read on the page for validator payouts.

What is the minimum stake necessary to be elected as an active validator?​

The minimum stake that is necessary to be elected as an active validator is dynamic and can change over time. It depends not only on how much stake is being put behind each validator, but also the size of the active set and how many validators are waiting in the pool.

There are a few ways to estimate the minimum stake.

One way can be to navigate to the Polkadot Apps Targets tab. The value at the top of the screen saying "Lowest" is the least staked validator. You need at least this much + 1 to enter the set.

You can also use some tools some to perform estimations.

  • Offline Election can provide exact results of running an election on the current set of validators using the same Rust code that is ran in Polkadot.

  • Validator stats script can give you an estimate that is based on the currently elected set, as well as some statistics about Kusama validators.

Why Polkadot targets 1000 validators while other projects have hundreds of thousands?​

Polkadot's goal to have 1000 validators is set to be something that is practically achievable in the short term with high confidence of good performance in a live environment. Furthermore, validators in Polkadot are not the only stakers, and if we consider the number of stakers that can be possible on Polkadot the number can scale up to hundreds of thousands. Since validators are performing critical consensus work to maintain the security of the chain including all of its shards, a more modest number of validators is estimated to start. Upon later improvements, such as implementing signature aggregation for finalization messages, the number of validators could reasonably scale up. However, increasing validators above one thousand remains a goal for later iterations of Polkadot.

Additionally, other projects sometimes have a different definition of validator that approximates more closely to remote signing keys without the full operation of a validating node. On Polkadot, each validator is running their own validating node and performing full verification of the Relay Chain, voting on finality, producing blocks in their decided slots, and verifying parachain state transitions. Other projects may consider validators and "validating nodes" as separate entities.

Finally, individuals may participate in the block production process indirectly by nominating validators. In this way, individuals who are not running a node can still share in staking rewards.

Relay Chain​

What is the block time of the relay chain?​

Both the Kusama and Polkadot networks are currently operating at a rate of one block every six seconds.

This may be changed in the future. It may go as low as two to three seconds after optimizations, or potentially increase in order to handle the capacity of the parachain networking in a live environment.

Does Polkadot have smart contracts?​

No - and yes. The Polkadot relay chain does not implement smart contracts natively. The reason for not having smart contracts on the relay chain is part of the design philosophy for Polkadot that dictates that the relay chain should be the minimal logic required to accomplish its job.

While the Polkadot relay chain does not implement smart contracts directly, there are numerous parachains that do. It's possible for parachains to enable smart contract functionality and then benefit from the security and interoperability features of Polkadot. Additionally, existing smart contract chains can connect to Polkadot as a parachain, or via a bridge.

So it's better to say that the Polkadot ecosystem has smart contracts versus "Polkadot has smart contracts."

How does the Polkadot relay chain connect to external chains in the ecosystem?​

One of the cornerstone interoperability technologies being researched and developed for deployment on Polkadot is cross-chain bridges. Bridges come in a variety of flavors with varying levels of trust associated with them. Polkadot is predominantly researching the trust-minimized flavor that imposes economic costs on the operators of the bridge, and therefore makes it economically secure. Bridge efforts are being worked on in concert with other projects in the ecosystem.

What is Polkadot's Transactions Per Second (TPS)?​

Polkadot is a heterogeneous sharded network comprising a relay chain and numerous parachains, which are all individual blockchains built on Substrate executing in parallel. Hence, the Transactions Per Second (TPS) of Polkadot is a number that encompasses all the transactions on the relay chain as well as parachains. As the transactions on these Substrate-based blockchains are weights based, it makes sense to use TPS as a measure for the network performance if all the transactions carry the same weight. Performance benchmark tests show that Substrate-based blockchains can achieve over 1000 TPS for balance transfer transactions. Assuming Polkadot is running over 100 parachains; the projected TPS is well over 100,000. With asynchronous backing upgrade, the TPS is expected to increase tenfold to 1,000,000.

It is essential to realize that TPS is inherently a subjective measurement with numerous factors that can contribute to it. It's hard to gauge the usefulness of TPS in isolation (when compared to other chains), as it depends on what a transaction does for a particular network. To view how Polkadot measures TPS see the Polkadot sTPS (Standard Transaction Per Second) to consider precisely how benchmarking was performed for Polkadot.

DOT​

What is the difference between DOT (old) and new DOT?​

The DOT (old) unit on Polkadot was at twelve decimal places, otherwise known as 1e12 Plancks. On 21 August, 2020, Denomination Day, the DOT (old) value was redenominated to 1e10 (10_000_000_000, or ten billion) Plancks, meaning that the new DOT was valued at ten decimal places. Following the redenomination, the new DOT is called DOT.

What is the inflation rate of the DOT?​

The inflation rate is approximately 120,000,000 DOT per year.

The 85% of inflation is rewarded to validators for performing their duties, while the 15% goes to the treasury. Please see the article on inflation for more information.

Why can't crowdloaned DOT be staked?​

DOTs contributed to a successful crowdloan campaign by a parachain are bonded for the entire lease period, which is two years on Polkadot. The crowdloaned DOT cannot be used for any other DOT utility functionalities like staking and democracy. In exchange to the lost staking rewards or liquidity of DOTs, the parachain team may offer rewards to the contributor.

The utility of crowdloaned DOT is to provide a lease for a parachain. The utility of staked DOT is to secure the network through a reward/slash mechanism. Allowing crowdloaned DOT to be staked results in complex consequences like applying a slash on crowdloaned DOT that was meant to be bonded for the entire lease period of a parachain. In a way, the inaccessibility of crowdloaned DOTs and the lack of staking rewards for the entire lease duration encourages the contributors to back projects that are valuable to the ecosystem.

Governance​

What prevents Polkadot governance from failing?​

Polkadot's governance has already been shown to work. Examples can be found in the runtime upgrades that have successfully taken place through on the testnets as well as in a real economic environment on Kusama and Polkadot itself.

It is fair to say that the field of on-chain blockchain governance is still new, and no one can claim to know exactly what the optimal version of on-chain governance is yet. However, Polkadot takes a brave step forward in pioneering thought-through mechanisms for evolving a blockchain.

Blockchains need a method to adapt and evolve. Therefore, an on-chain governance system was necessary for the long-term success of Polkadot. Ultimately, it is the token holders that are responsible for preventing Polkadot's governance from failing by using their economic value and conviction to sway the progression of the protocol.

What prevents Polkadot governance from becoming plutocratic?​

A savvy reader might have noticed that the answer to the previous question endowed the token holder with the ultimate responsibility to ensure that Polkadot's governance does not fail. By following the train of this assertion, one might assume that Polkadot's governance is susceptible to becoming ruled by a few large token holders (called whales in trading parlance) and therefore become a mere plutocracy (rule of the rich).

There are several other mechanisms that are built-in to the governance system to resist this plutocratic tendency. One of these mechanisms is called conviction voting, and imbues greater voting power to token holders who are willing to lock their tokens on the protocol for longer lengths of time. Longer lock-ups display conviction in a vote. Conviction voting could allow a highly determined minority to overrule the vote of an apathetic majority in certain situations. Another mechanism is known as Adaptive Quorum Biasing. This makes proposals have a varying threshold for approval or rejection based on what part of the governance protocol the proposal originated in. For details on the subtleties of Polkadot's governance system, please see the governance page.

Parachains​

How do parachain economics work?​

Parachains have the flexibility to implement their own monetary system or incentive structure for collators. However, this is not strictly necessary. Since the collator's job is to continue to give recent state transitions to the validators on the relay chain who validate each transition, the security of the parachain and the Polkadot network is completely separate from parachain economics. Parachains need collators to continue to progress, so it wouldn't be unreasonable to see them incentivize collator nodes in some way, but the specific mechanism is completely up to parachain implementers.

Are parachains ephemeral? What happens when a parachain fails to renew its coretime?​

Parachains are not ephemeral. As long as someone is keeping the data for a parachain, the parachain can move between being a parachain, an on-demand parachain, or a separate sovereign chain at different points of its lifetime. Especially with on-demand parachains, parachains can produce blocks when their usage and throughput makes it necessary.

When a parachain could not renew its bulk coretime and needs to keep its chain live, there are a couple of options to consider. One option is to explore secondary coretime marketplaces on Lastic or RegionX. The other option is run as an on-demand parachain, and purchase coretime to produce one block at a time. On-demand parachains are still secured by the relay chain but don't need to hold a core and can produce a block when it's economically feasible for them. For more information, please refer to the parachains page.

Networking​

What is libp2p?​

Libp2p is a modular and extensible networking stack that is used by IPFS, Substrate, and many other projects. It is a collection of peer-to-peer protocols for finding peers and connecting to them. Its modules have logic for content routing, peer routing, peer discovery, different transports, and NAT traversals. It is intended to be used by applications for building large scale peer-to-peer networks by only selecting the parts of the protocol suite that are needed.

The Rust implementation of the specification was built and primarily maintained by a team of contributors at Parity Technologies. The Go and JavaScript versions are maintained by Protocol Labs as well as community contributors. A Nim version of the library also exists. Libp2p as a whole is an open source project that is actively developed and expanded on various code repositories hosted on their GitHub.

Does Polkadot use libp2p?​

Yes, since Polkadot is built with Substrate. Substrate uses a networking protocol that is based on libp2p (specifically the Rust libp2p library). However, Substrate uses a mix of standard libp2p protocols and protocols that are homegrown and not official libp2p standards. Of the standards protocols, those which are shared with other implementations of libp2p such as IPFS, are connection-checking (ping), asking for information on a peer (identity), and Kademlia random walks (kad).

Of the protocols that are custom to Substrate, there are the legacy Substrate stream, a request-response for getting information on blocks (sync), a light client protocol, a notification protocol for transactions, and block announcement. For detailed information on how Substrate uses libp2p and the standard and custom protocols, please see the networking documentation.

How does libp2p differ from IPFS?​

The Interplanetary File System (IPFS) is a peer-to-peer hypermedia protocol used primarily for storage of files. It allows one to upload a file onto the network and share it with its content addressable URI. IPFS, like Substrate, is an application of libp2p and exists higher on the technology stack. Although both IPFS and Substrate use libp2p, it cannot be said that Substrate "uses" IPFS since besides sharing the underlying library for networking there is no native integration between the two applications.

Kusama​

What is the minimum amount of KSM / DOT I can have in my account?​

Please see information about Existential Deposits.

What are the transfer fees for Kusama?​

It is important to note that the cost of transferring KSM is dynamic. Currently, the minimum cost of transferring KSM is 0.01 KSM (the base fee), although this can be changed via governance. However, actual transaction fees vary based on a variety of factors. Specifically, fee calculation follows the following formula:

base_fee + (tx_length * length_fee) + WeightToFee(weight)

Please see the fee calculation page in the Substrate documentation for more detailed information.

Answered by Gav series​

The "Answered by Gav" series is a collection of posts uploaded to Reddit of questions that have been asked in the Polkadot Watercooler Riot channel and answered by Polkadot founder Gavin Wood.

Last updated on by Filippo