Skip to main content

Warp Centralized Sequencer


This section describes the operation of the current centralized sequencer, which will soon be replaced by the new decentralized solution.

How it works

Instead of posting the interaction transactions directly to Arweave mainnet, Warp SDK creates a data item with interaction input and tags which is then signed with user's wallet. Data item is then sent to Warp Sequencer (/gateway/v2/sequencer/register endpoint) (this is the default behaviour of Warp's SDK contract.writeInteraction function, when forMainnet instance is being used).

The Warp Sequencer then:

1. Generates a sort key

A sort key is generated from:

  1. current mainnet network height
  2. current sequence value
  3. original transaction id
  4. current mainnet block hash

In the original SmartWeave protocol specification, a sort key is defined as a [ block_height,sha256(transactionId + blockHash) ], where:

  1. block_height - current network height, l-padded with 0 to 12 chars, e.g. for block height 1015556, the result is 000001015556
  2. sha256(transactionId + blockHash) - a sha256 hash of the concatenated buffers of the transaction id and block hash, e.g. for txId UR_35HORbjjZ_NnUqinkZuWkcNB1-gBST3Rezt5JrDs and block hash ixWCxRN36DjVUxQRa68xIeoZLfvLDTtX78e0ae8RAAJjOPpDBuVKVaEKYOpq7bLS, the result is 44edd70f2018924f22a878a558a8f2d5cae8bc1f718d567df43bf52b6384d260.

The complete sort key for the above values would be: 000001015556,44edd70f2018924f22a878a558a8f2d5cae8bc1f718d567df43bf52b6384d260.

The generated sort keys are then used by the SmartWeave protocol to lexicographically sort the transactions.

The Warp Sequencer extends this default mechanism by the current sequence value.
The formula for the sort key is extended to: [ block_height,sequence_value,sha256(transactionId + blockHash) ]

This sequence value can be obtained from the Sequencer's node timestamp, database or other sources. In its current implementation - a Sequencer node timestamp value is being used.
This in effect gives a fair transactions ordering - the transactions will have the sequence assigned in order in which they are processed by the Sequencer.

Assuming transaction id La_NpAFAWxGj-VIiLfg7NbBfox0RZ8uuEJSOOZykd48, block hash -o88tFYsMG9RXSGcNXX5sVDuSV5uHy7zuFRj6vYo91e3mXpmng6qw322Ip0-EguA, block height 1015560 and current Sequencer value 1663069424541, the generated sort key would be 000001015560,1663069424541,a21ac8a60326ba8c2bb8caa05cff3334a22e9960ef55de0b5392caa30b484d0a

NOTE All the transactions sent to Arweave directly, have the sequence value assigned to 0000000000000000. This effectively means that if transactions to a given contract are sent both directly to Arweave mainnet and Warp Sequencer - if two transactions happen to be at the same block height, the "direct" Arweave transactions take precedence. This also means that the sequencing algorithm is fully backwards compatible with the original SmartWeave protocol.

2. Generates tags for the Bundlr transaction

Tag NameTag Value
Sequencer-OwnerThe original owner/signar of the contract transaction
Sequencer-MillsThe sequence value used by the Sequencer for this transaction
Sequencer-Sort-KeyThe generated sort key for this transaction
Sequencer-Prev-Sort-KeyThe sort key of the previous transaction
Sequencer-Tx-IdThe original transaction id
Sequencer-Block-HeightThe block height used for generating the sort key
Sequencer-Block-IdThe block hash used for generating the sort key
Sequencer-Block-TimestampThe timestamp of the block that was used for generating the sort key
...all the tags of the original transaction

The Sequencer-Prev-Sort-Key tells what is the sort key of the 'previous' transaction in the sequencer and can be used to verify whether all transactions have been properly loaded (i.e. if one decides to load them directly from L1 nodes) and none is missing.

Additional set of tags are added in case user requests generating a random value using VRF (Verifiable Random Function):

Tag NameTag Value
vrf-indexThe original hash generated by the VRF (using sort_key as input data)
vrf-proofThe original proof generated by the VRF
vrf-bigintA BigInt value evaluated from the hash generated by the VRF
vrf-pubkeyThe public key used by the VRF

Verifiable randomness can be used by contracts that require using random values - e.g. gaming contracts, nft/loot generating contracts, etc. Using the sort_key, vrf-proof and vrf-pubkey, the client can always verify the generated random value.

3. Wrap original data item in a bundle and uploads the bundle to Bundlr

Apart from all the tags from point 2, some additional tags are added to the wrapping bundle:

Tag NameTag Value

In order to send original data item to Bundlr, we use the concept of nested bundles and set an interaction data item inside a bundle. If you're not faimiliar with this concept, here is a quick summary:


Bundling allows to write multiple data items into one top level transaction. A data item differs from a regular transaction by not allowing to transfer AR tokens and passing reward but it has most of the transaction's properties - such as owner, data, tags, owner and id.

In a nutshell, the nested bundles concept means that a data item of a bundle can also be a bundle containg other data items. According to ANS-104 standard it can lead to theoretically unbounded levels of nesting.

You can read the specification for nested bundles standard in ANS-104.


Obviously the data-item is signed by the Sequencer's wallet - and as such can be easily verified. The Sequencer wallet address is jnioZFibZSCcV8o-HkBXYPYEYNib4tqfexP0kCBXX_M.

NOTE The original data item is not modified in any way - this is to preserve the original signature!

After receiving proper response and receipt from Bundlr, the Warp gateway indexes the contract interaction internally - to make it instantly available.

4. Finally, the Warp gateway returns the response from the Bundlr to the client.

Interaction data item retrieval (generated by the Warp Sequencer) via Arweave gateway

Use the GQL endpoint, with the original data item id passed in the Contract tag. Note that all the interactions will be part of a bundle (i.e. will have the value set).

query {
ids: ["1UIhK4vL5lc2X4aMsJFmMpJqfdgrjznVzi2F17yLBlc"]
) {
edges {
node {
tags {
block {
bundledIn {

Interaction retrieval via Warp gateway

The Warp /gateway/interactions/:id endpoint allows to retrieve the interaction info based on its original id.