Email flows (welcome, abandoned cart, win-back)
Flow runs depend on the segmentation engine, which routinely takes 15-25 minutes — sometimes hours — to recalculate even for simple lists.
What people actually say
✕Klaviyo Support tells customers that segment updates taking up to 15 minutes are considered normal, and there is no SLA on faster propagation for time-critical flows.
Source: Klaviyo Community, segments slow lately ↗✕Users report segments stuck at 0.1 percent for several minutes before calculating, and suppression list uploads of a few thousand addresses taking over an hour to complete.
Source: Klaviyo Community, segments slow lately ↗✕The flows editor periodically forces users back to a legacy UI to drag in blocks or images, with Klaviyo support routinely recommending cookie clears as the fix.
Source: Klaviyo Community, trouble editing flows ↗
Flows run on a durable queue (Inngest or BullMQ) where every step is a typed function with retries and idempotency keys. Triggers fire off Shopify webhooks the second the event lands — no 15-minute segment lag — and sends go through Amazon SES or Resend at fractions of a cent per email. Branches are code in a PR, dry-runs replay against production data.