Klaviyo BFCM Segments: How Fast They Update Before a Send

A segment created or edited the day before a BFCM send raises two questions: has it finished updating, and will the campaign read it up to date? Klaviyo documents the update delays and the moment a campaign locks its recipients. This article puts them end to end to set a cut-off time for edits.

TL;DR. Klaviyo processes most segments in close to real time, but a manual update can take up to 15 minutes and a monitored segment up to an hour. A relative time condition can add or remove a profile through the passage of time alone, once every 24 hours. Finally, a campaign determines its recipients at scheduling (the default setting) or shortly before sending, and later changes may not be included.

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How Klaviyo updates a segment

The page on segment updates describes a segment as a dynamic group of profiles: once the definition is set, Klaviyo adds and removes profiles depending on whether their interactions match the conditions (Klaviyo, understanding how segments update). Segmentation requests are processed as close to real time as possible: a customer who places an order or opens an email joins the segment shortly after.

The page adds that, in some cases, a high volume of segmentation requests across Klaviyo's customer base can cause delays. In our view, that is a reason not to aim for the last minute in a BFCM calendar, since the page does not say which days or how long the delay lasts.

One point to watch: inactive segments stop updating. If a segment in your list has been deactivated, reactivate it before expecting membership changes.

The delays written in the page

The page gives two windows:

1. If you update a segment manually, processing can take up to 15 minutes.
2. If you are monitoring a segment, updates can take up to an hour.

Beyond these windows, the page tells you to check Klaviyo's status page or contact support.

The page says "up to", not an average delay: we give no typical delay.

Relative time conditions: once every 24 hours

A segment can change members without the profile doing anything, when its condition is relative. The page gives the example: "in the last 30 days" is relative since the timeframe constantly changes, whereas "before January 1, 2025" is not.

Two cases coexist:

1. A profile that takes an action qualifying (or disqualifying) them is added or removed as close to real time as possible.
2. A profile that qualifies or stops qualifying through the passage of time alone is added or removed once every 24 hours.

The page's example: in a segment of "at least 1 purchase in the last 30 days", a buyer is added as close to real time as possible, but someone who does not buy again is removed on day 31, once per day, because there is no event triggered by not purchasing. A segment of people who purchased between 30 and 60 days ago also updates once every 24 hours, as it cannot be computed from a purchase event in real time in every case.

In our view, the consequence for a BFCM segment is simple: if the purchase window must be exact on a given date, a condition between two fixed dates avoids the "once a day" effect. Our article on last year's BFCM buyers details this choice of dates and time zone.

Forcing a manual update

The page describes the steps:

1. Go to Audience > Lists & segments and open the segment.
2. Click Edit definition.
3. Click Update segment. The conditions can stay unchanged to simply refresh membership.

The page warns that a manual update does not automatically add the segment's members to segment-triggered flows. If a BFCM flow starts from a segment, refreshing it does not replace the normal entry into the flow.

Preview before saving

Before you create a segment, Klaviyo lets you preview its membership (Klaviyo, how to preview segments). The Preview details button opens a sidebar with the segment's estimated size and a selection of sample profiles. The page states that these counts are estimates: slight differences can exist with the final size. Incomplete or invalid criteria can also be left out of the preview count.

When does a campaign read the segment?

An up-to-date segment is not enough: the campaign must also read it at the right time. Klaviyo offers two options for single-channel campaigns (Klaviyo, how to change when a campaign's recipients are determined):

• At time of scheduling (the default setting): Klaviyo takes a picture of your lists or segments shortly after the scheduling request completes. Later changes may not be included, and people added afterward do not join the campaign.
• At send time: the picture is taken once, shortly before the campaign's first messages go out. It includes changes made before recipients are finalized. No one is added afterward, including for later sends in recipients' local time zones.

The page specifies that "At send time" may use more sends (or more Mobile Messaging spend) than planned, or even trigger an automatic upgrade or require a plan upgrade. Owners, Admins, Managers, and Campaign Coordinators can change the account default, which does not update campaigns already created. For a Fixed send time campaign, the Determine recipients at send time option overrides it campaign by campaign; Gradual send does not offer this option. The account setting is found under Settings > General > Messaging > Campaign sending defaults.

Our article on BFCM campaign audiences details the exclusions and overlaps that apply to this picture.

Estimated audience and segment size

A third page explains the gaps between numbers (Klaviyo, understanding segment counts and estimated audiences). The campaign builder shows estimated recipients, not the raw segment size: the estimate applies suppression, whether a profile can receive marketing on the channel, and the excluded lists and segments. Smart Sending, when enabled, is checked at send time and can reduce the number of messages sent further.

A segment edited shortly before the send: order of operations

These steps combine the pages above. This is Deliver's reading: no page describes this scenario from end to end.

1. Edit or create the segment, then run Update segment without waiting for the next automatic pass.
2. Allow up to 15 minutes before relying on the count, and check Klaviyo's status page if the delay is exceeded.
3. Check the count in Lists & segments, then the recipient estimate in the campaign builder.
4. Schedule the campaign once the segment is stable. If the default setting is kept, changes made after scheduling may not be included: do not assume they appear in the campaign.

Our BFCM email send calendar lets you set a cut-off time for segment edits before each send. The Klaviyo BFCM guide brings the whole preparation together.

Checklist before BFCM

These points are Deliver's advice.

1. Each campaign segment has an edit cut-off time, well before the send time.
2. The "when recipients are determined" setting is checked before the first campaign.
3. One person compares the segment count and the campaign builder's estimate before each scheduling.

FAQ

How long does a segment take to update?

Klaviyo processes most segments in close to real time. The page says that if you update it manually, it can take up to 15 minutes, and that for a monitored segment it can take up to an hour.

Why does a profile stay in a "last 30 days" segment?

If the profile stops qualifying through the passage of time alone, it is removed once every 24 hours. The page cites the example of a removal on day 31.

Does a manual update trigger a segment-based flow?

No. The page states that a manual update does not automatically add the segment's members to segment-triggered flows.

Does a scheduled campaign read changes made afterward?

It depends on the setting. With "At time of scheduling" (the default), later changes may not be included. With "At send time", the picture is taken shortly before the first messages go out.

Want an outside view on your segments before the peak? We run Q4 readiness audits, or you can talk directly with the Deliver team.