# Engineering Sync Readout - 2025-08-26

**URL:** https://collective.flashbots.net/t/engineering-sync-readout-2025-08-26/5213
**Category:** BuilderNet
**Created:** [August 27, 2025, 2:42pm UTC](https://collective.flashbots.net/t/engineering-sync-readout-2025-08-26/5213 "2025-08-27T14:42:49Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![metachris](https://collective.flashbots.net/user_avatar/collective.flashbots.net/metachris/32/6_2.png) [@metachris](https://collective.flashbots.net/u/metachris)
#### Post date: [August 27, 2025, 2:42pm UTC](https://collective.flashbots.net/t/engineering-sync-readout-2025-08-26/5213/1 "2025-08-27T14:42:49Z")

</div>

This is a brief readout of the BuilderNet Engineering Sync on 2025-06-26. That meeting is a place for operators to discuss all kinds of technical topics, from current development, ideas, issues, designs and architecture to longer term roadmap and architecture.

1. **Forced Azure Gen6 migration**
  - Azure rushes a deprecation of Gen5 TDX instances and requires a migration to Gen6 by Sept. 12, 2025 (after which Gen5 instances will not boot/reboot anymor).
  - We tested the latest [cvm-proxy](https://github.com/flashbots/cvm-reverse-proxy) with TCB level override, works fine . Will merge soon, tag and deploy. 🎉
  - This update may be needed because Azure often provides instances with an outdated seamloader. Currently the ratio is about 1:5 outdated:up-to-date.
  - Two upgrade options: (a) deploy v1.5 release with patches, (b) finalize new v1.5.1 release.
  - We will see if finalizing and testing a new image is viable, in which case we will go with option b - new release. Otherwise we still fall back to option a.
  - Operators need to check/request Gen6 Azure quota in relevant locations (ECEV5 vs ECEV6 quota)

2. **Top bid stream**
  - Upgrading top-bid collector, which receives bids from the relays and informs the bidding.
  - Tests look good and ready for production promotion.
  - [Code is in the rbuilder codebase.](https://github.com/flashbots/rbuilder/tree/develop/crates/bid-scraper)
  - Seeing an unusual 4ms delay from scraping → update. Unclear where it’s coming from, will take a look at it.

3. **Mempool tx optimizations**
  - Is currently being tested, looks all good with 50 blocks history (instead of 5). Will roll out to production on next update cycle.

4. **Refunds to non-EOA addresses**
  - Double-checking actual gas limit of payout to refund address.
  - Once confirmed it’s 21k then we’ll remove the contract limitation.

5. **Orderflow sharing observability**
  - Right now there is a lack of visibility into timings of transaction propagation across BuilderNet.
  - Working on a design doc for bundle recepts, so each node could record just when they saw which bundles.
  - We do have several metrics for orderflow proxy latency when sending to other builders, but that’s not enough.

6. **Measuring relay latency**
  - Working on better visibility into relay latency. We don’t yet have clean metric for it, currently it also includes simulation time.

7. **Per-bundle refund API**
  - There already is an API per bundle: [flashbots\_getFeeRefundsByBundle](https://docs.flashbots.net/flashbots-auction/advanced/rpc-endpoint#flashbots_getfeerefundsbybundle)
  - Checking whether this is enough or if more data is needed