Replication lag

Type a segment and hops. 5 and 3 give 15 ms. 20 and 2 give 40 ms. 8 and 1 give 8 ms. Segment times hops, not measured apply lag.

This is segment_ms × hops. Not measured apply lag from a replica. IOPS from a queue sits on queue depth.

Input data

Additional options (optional)

Results

Enter data and click Calculate.

Percentiles (p50, p95, p99)

Percentiles: a value, a percentile, and an optional baseline.

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Queue depth vs latency

Queue depth: depth and latency.

Use calculator →

How it works

Replication lag in this calculator multiplies a segment by hops. 5 ms and 3 hops give Łączne opóźnienie łańcucha: 15 ms. 20 and 2 give Łączne opóźnienie łańcucha: 40 ms. 8 and 1 give Łączne opóźnienie łańcucha: 8 ms. This is not apply lag from a replica.

Field replication-lag-a is segment ms. Field replication-lag-b is the hop count. 5 × 3 = 15. 20 × 2 = 40. 8 × 1 = 8. Field replication-rpo-ms in the first two examples is 50 and 30, but the result stays the chain sum.

15 ms does not come from Seconds_Behind_Source. 40 ms is not pg_stat. 8 ms is not apply from WAL. You type the segment and hops. The calculator does not read a replica.

Queue depth next door counts IOPS from ms. Percentiles label a pN. Here 5 and 3 stay 15 ms, the chain product alone.

Type 5 and 3, then Calculate. The result is Łączne opóźnienie łańcucha: 15 ms. A comma in 5,5 works. Zero hops leaves 0. This is not a live replica.

5 and 3 give 15 ms. 20 and 2 give 40 ms. 8 and 1 give 8 ms. Another segment at 3 changes 15 ms.

Formula

lag = segment_ms × hops. A chain product, not measured apply lag.

How to use

  1. Type segment 5 and 3 hops.
  2. Click Calculate. The result is Łączne opóźnienie łańcucha: 15 ms.
  3. 20 and 2 give 40 ms. 8 and 1 give 8 ms.
  4. Segment times hops, not apply lag.
  5. IOPS from ms sits on queue depth.

5 ms and 3 hops = 15 ms

Segment times hops. 5 and 3 give 15 ms. This is not apply lag.

Replication
The same chain. 20 and 2 give 40 ms. 8 and 1 give 8 ms.
lag
The chain product. 5 and 3 leave 15 ms. Not Seconds_Behind_Source.
hops
Field replication-lag-b. 3 at 5 ms leaves 15 ms. Not apply.

Examples

Example 1

  • segment 5 ms
  • 3 hops
  • RPO 50 ms

Łączne opóźnienie łańcucha: 15 ms

How many ms at 5 and 3 hops? Łączne opóźnienie łańcucha: 15 ms. Segment times hops, not apply lag.

Example 2

  • segment 20 ms
  • 2 hops
  • RPO 30 ms

Łączne opóźnienie łańcucha: 40 ms

What about 20 and 2? Łączne opóźnienie łańcucha: 40 ms.

Example 3

  • segment 8 ms
  • 1 hop

Łączne opóźnienie łańcucha: 8 ms

What about 8 and 1? Łączne opóźnienie łańcucha: 8 ms.

Common questions

How many ms at 5 and 3 hops?

Łączne opóźnienie łańcucha: 15 ms. 5 × 3. Not apply lag.

What about 20 and 2?

Łączne opóźnienie łańcucha: 40 ms. 20 × 2.

What about 8 and 1?

Łączne opóźnienie łańcucha: 8 ms. One hop leaves the segment.

Is this measured apply lag?

No. Two fields. The calculator does not read Seconds_Behind_Source.

Why RPO?

Optional replication-rpo-ms for a comparison. The result stays the chain sum.

Does a comma in 5,5 work?

Yes. 5,5 and 3 give a different chain than 5 and 3.

Is 15 ms a live replica?

No. A result from a segment and hops. Not WAL.

Where do I time IOPS from ms?

On queue depth. Here 15 ms from 5 and 3 stays.

Does zero hops count?

Yes as 0 ms. A blank field is a number error, not measured lag.

Knowledge sources

The calculator counts bits, bytes or throughput from your numbers. Below are SI and bit definitions (NIST).

Page updated in 2026.