# Segment Build Time Warning **URL:** \ **Category:** Mautic 5 Install/Upgrade Support\ **Tags:** discussion\ **Created:** [June 5, 2025, 8:46am UTC](https://forum.mautic.org/t/segment-build-time-warning/35799 "2025-06-05T08:46:07Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![dirk\_s](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/dirk_s/32/748_2.png) [@dirk\_s](https://forum.mautic.org/u/dirk_s)\ **Post date:** [June 5, 2025, 8:46am UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/1 "2025-06-05T08:46:07Z")
We run a Mautic with more or less 10.000 contacts. Some of the segments (with combination of segments as well) have build time warnings… a segment with 5.185 resulting contacts took 544 seconds. What are the limiting factors for the segment building? We didn’t see this issue before. System has 512MB RAM. ---
**Author:** ![joeyk](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/joeyk/32/11164_2.png) [@joeyk](https://forum.mautic.org/u/joeyk)\ **Post date:** [June 11, 2025, 5:14am UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/2 "2025-06-11T05:14:39Z")
If you use “Member of a segment” - that is one of the heaviest querries in Mautic. Is this an upgraded Mautic where the previous version ran okay? J ---
**Author:** ![dirk\_s](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/dirk_s/32/748_2.png) [@dirk\_s](https://forum.mautic.org/u/dirk_s)\ **Post date:** [June 11, 2025, 12:52pm UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/3 "2025-06-11T12:52:22Z")
Hi Joey, thanks for looking into it - I don’t have comparisons, as its a relatively young installation. But I did some analysis, into a spreadsheet and let it analyse. Looks like “was sent a specific mail” seems to be the biggest culprit of long runtimes? Member of a segment is an important filter we also used in those segments (including, excluding - even combined) but seems not to be the main reason - at least in that screened examples. ### 🧠 Key Takeaways: - **“Was sent a specific mail”** is the **only filter type clearly overrepresented in slow segments**. It appears in 100% of long-running segments and only in 50% of fast ones. - Other filters like **“tags”** , **“company\_preferred\_locale”** , and **“Stufe”** only appear in the faster segment group. - **“Segment Membership”** is common in both but slightly more frequent in fast segments, suggesting it’s not a strong contributor to slowness. ### 📌 What This Means: - **Email interaction filters** (e.g., _“Was sent a specific mail”_) are likely **performance bottlenecks** – probably due to heavy joins or historical data scans. - You might consider optimizing these segments by: - Preprocessing such data into a **custom field or tag** , then filtering based on that. - Reducing the number of emails checked, or checking only for **more recent interactions**. ---
**Author:** ![joeyk](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/joeyk/32/11164_2.png) [@joeyk](https://forum.mautic.org/u/joeyk)\ **Post date:** [June 11, 2025, 1:24pm UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/4 "2025-06-11T13:24:30Z")
We have a 1.5 million Mautic, where we did a bunch of indexes, and that helped tremendously. It’s really fast. ---
**Author:** ![dirk\_s](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/dirk_s/32/748_2.png) [@dirk\_s](https://forum.mautic.org/u/dirk_s)\ **Post date:** [June 11, 2025, 9:18pm UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/5 "2025-06-11T21:18:32Z")
Did you add indexes manually on database level? ---
**Author:** ![joeyk](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/joeyk/32/11164_2.png) [@joeyk](https://forum.mautic.org/u/joeyk)\ **Post date:** [June 12, 2025, 8:11am UTC](https://forum.mautic.org/t/segment-build-time-warning/35799/6 "2025-06-12T08:11:26Z")
Yes, because segment membership, email\_stats cannot be added in the UI