Tacnode™
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The Peak-Hour Lag

The health check is green, and the replica is falling behind anyway.

Quiet hour. Replica lag is a fraction of a second.

What’s true
2
The read replica
2
reads
Decision
Approve the next attempt?
waiting

Illustrative figures.

Where this shows up

Velocity and abuse checksThe count trails the attempts during a burst.
Rate limitingA limit applied to traffic as it was several seconds ago.
Market-open exposurePositions read from a copy in the first busy minutes of the session.
Promo abuseOne account redeems a code faster than the replica can count it.

Why the read replica gets it wrong

trafficreplica lagCHECK RUNS: SEES 3 OF 9the lag peaks with the traffic

Every replica falls behind at the peak; that’s how replication behaves under heavy writes. More replicas give you more read capacity, and each one comes with its own lag.

By the time the decision ran, its context was outdated. We call that a context gap.

Add read capacity without adding copies.

trafficno lag of its own to chaseSHARED STORAGEreaderreaderreadermore readers on the same storage

Tacnode keeps the counts your checks read current at peak, and every service reads the same ones. When you need more read capacity you add nodegroups over the same storage, rather than another copy that can fall behind.

What comes inSource data arrives via change streams, and decision state is written to Tacnode.
What staysYour source databases don’t change.
What the decision getsNo replica lag to chase during the busiest minutes.
If an engineer asks how

Read capacity scales out with nodegroups over shared storage. Velocity counts are computed on demand against current data, or kept as views refreshed on a schedule you set.

Questions to put to your team

  1. What does replica lag look like in your busiest minute of the day?
  2. Which checks read from a replica?
  3. How would you find out a check undercounted?

Is your velocity check telling this lie?

Bring it to a demo, and we’ll trace what it reads and how old that data is by the time it runs.

Book a demo →
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