> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cdp.coinbase.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Exchange FIX Best Practices

## Optimize Traffic

To optimize your FIX set up, spread traffic over as many portfolios as possible to minimize order-entry latencies.

You should adhere to the following:

* `1` API key per session/connection to guarantee a connection
* `75` maximum connections per profile
* `175` maximum connections per user across all profiles

## Batch Messages

We strongly recommend batch messages for both order entry and cancellation.

Batch Requests:

* Can have up to `15` orders / cancels per request.
* Only count for a single message for the purposes of rate limiting.
* Can be more efficient to process compared to the equivalent individual requests.

Available batch messages are:

* [New Order Batch (U6)](/exchange/fix-api/order-entry-messages/order-entry-messages5#neworderbatch-35%3Du6)
* [Order Cancel Batch Request (U4)](/exchange/fix-api/order-entry-messages/order-entry-messages5#ordercancelbatch-35%3Du4)
* [New Order Batch Reject (U7)](/exchange/fix-api/order-entry-messages/order-entry-messages5#neworderbatchreject-35%3Du7)
* [Order Cancel Batch Reject (U5)](/exchange/fix-api/order-entry-messages/order-entry-messages5#ordercancelbatchreject-35%3Du5)

## Modify Order Requests

We strongly recommend Modify Order Requests where applicable.

Modify Order Requests:

* Keep your place in the order book queue when size is amended down.
* Result in 50% fewer messages when compared to canceling an existing order and placing a new one.
* Reduce your overall rate limit usage when compared to sending a cancellation followed by a new order.
* Can be more efficient to process compared to the equivalent individual cancel and new order requests.

For rate limits, see [FIX API Rate Limits](/exchange/fix-api/rate-limits).

## Drop Copy Session

Enabling `DropCopyFlag="Yes"` (`9406=Y`) configures your session to receive execution reports across all active sessions for the same profile.

We recommend that you enable DropCopyFlag on a **separate, read-only session**:

* Execution latencies are higher for Drop Copy sessions because the same connection handles more read traffic.
* Multiple Drop Copy sessions produce multiple copies of redundant data.