Exchange Sharding

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Overview

Kalshi splits trading across multiple matching engines to scale capacity. Exchange instances correspond to specific categories (e.g. “crypto” or “combos”). Kalshi plans to add shards incrementally to maintain a healthy balance of traffic.

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Balance Management

Kalshi’s collateralization checks run within the matching engine. Programmatic traders normally need to fund the relevant exchange shard before placing an order. FCM members can instead enable automatic collateral transfers on eligible FIX sessions. Funding Overview

• Account transfers can be made through the Intra Account Transfer API.
• Manual transfers are also available through the Kalshi UI.
• Get Balance provides a breakdown of account balances across exchange indexes.

Automatic Order Transfers on the App and Web Since the exchange sharding rollout, orders placed through the Kalshi App and Web automatically transfer capital between exchange shards as needed to fund the order. Market makers can disable this feature on the Exchange Indexes settings page. Subaccounts Overview

• To fund a subaccount on a new exchange instance, first transfer user-level funds to the desired exchange instance.
• Next, use Create Subaccount with the exchange_index parameter to provision the subaccount on the new instance.
• Then, use Transfer Between Subaccounts with the exchange_index parameter to transfer funds from the primary account to the subaccount on that instance.
• Get All Subaccount Balances provides a breakdown of subaccount balances for each (exchange_index, subaccount) pair.

Auto-Rebalancing

• Users may opt in to automatic rebalancing between exchange shards.
• The customer supplies a target balance allocation as a percentage of their balance across exchange shards. For example, {Default: 80, Combos: 20}.
• Every 10 seconds, Kalshi computes the customer’s balance on each exchange shard as its account balance minus the value of its resting orders.
• If the balance has drifted from the target allocation, Kalshi executes an intra-exchange account transfer on the customer’s behalf to restore the target allocation.
• Target balance allocations can be configured through the REST API and the clearing portal.

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Order routing

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Market Data

• The exchange_index field is provided on GET /markets, GET /events, and via the market and event lifecycle WebSocket streams for newly created events and markets.
• Market ticker formats are unaffected by exchange sharding. The exchange_index field is the authoritative source of truth.

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API2

The exchange_index query parameter is available on a per-endpoint basis.

• If exchange_index >= 0, routes directly to the target exchange.
• If exchange_index is -1, auto-routes using the required market_ticker.
• If exchange_index is omitted and market_ticker is provided, auto-routes using market_ticker.
• Otherwise, defaults to exchange index 0.

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FIX

ExDestination<100> is available on a per-message basis for event-contract sessions.

• If ExDestination<100> >= 0, routes directly to the target exchange.
• If ExDestination<100> is -1, auto-routes using the required market ticker in Symbol<55>.
• If ExDestination<100> is omitted and Symbol<55> is provided, auto-routes using Symbol<55>.

Sessions with UseCapReservation<21032> or automatic collateral transfers (AutoTransfer<21035>) enabled must omit ExDestination<100> or use -1 for new orders and replacements. Margined FIX sessions always route to exchange index 0.

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Series Shard Assignments

The following assignments determine the shard where new events are created. Shard 0 is the catch-all for all categories and tags not listed below.

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FAQ

• All child markets of an event will live on the same exchange instance.
• There is currently no plan to migrate any live market to a new exchange instance.
• Single REST order writes that explicitly target a nonzero shard are rate-limited against that shard’s Write budget. Auto-routed single REST order writes are billed to the unscoped Write bucket and every nonzero shard’s Write bucket. REST batch writes and explicit shard 0 writes use only the unscoped Write budget. See Rate Limits and Tiers.
• Providing ExDestination / exchange_index is unnecessary for all RFQ operations, including FIX QuoteRequest (35=R), Quote (35=S), and AcceptQuote (35=UA), which are routed internally by Kalshi.
• When trading via FIX, both MassCancelRequest and CancelOrdersOnDisconnect will target all exchange shards for the FIX session.
• Automatic routing will incur an additional latency cost.
• Subaccount balances are local to a specific exchange instance.
• Order groups do not function across exchange instances.
• KXMVECROSSCATEGORY-SHARD1-R is live in demo for testing.