diff --git a/doc/architecture/blueprints/cells/routing-service.md b/doc/architecture/blueprints/cells/routing-service.md
index ca1f1d3c52a72805460ff33cef93d52d254a3dce..9efdbdf3f916dfcf927527d07ce70fd5a8564809 100644
--- a/doc/architecture/blueprints/cells/routing-service.md
+++ b/doc/architecture/blueprints/cells/routing-service.md
@@ -65,7 +65,7 @@ For example:
| Security | only authorized cells can be routed to | high |
| Single domain | e.g. GitLab.com | high |
| Caching | can cache routing information for performance | high |
-| Low latency | small overhead for user requests | high |
+| [50 ms of increased latency](#low-latency) | | high |
| Path-based | can make routing decision based on path | high |
| Complexity | the routing service should be configuration-driven and small | high |
| Stateless | does not need database, Cells provide all routing information | medium |
@@ -74,6 +74,106 @@ For example:
| Self-managed | can be eventually used by [self-managed](goals.md#self-managed) | low |
| Regional | can route requests to different [regions](goals.md#regions) | low |
+### Low Latency
+
+The target latency for routing service **should be less than 50 _ms_**.
+
+Looking at the `urgency: high` request we don't have a lot of headroom on the p50.
+Adding an extra 50 _ms_ allows us to still be in or SLO on the p95 level.
+
+There is 3 primary entry points for the application; [`web`](https://gitlab.com/gitlab-com/runbooks/-/blob/5d8248314b343bef15a4c021ac33978525f809e3/services/service-catalog.yml#L492-537), [`api`](https://gitlab.com/gitlab-com/runbooks/-/blob/5d8248314b343bef15a4c021ac33978525f809e3/services/service-catalog.yml#L18-62), and [`git`](https://gitlab.com/gitlab-com/runbooks/-/blob/5d8248314b343bef15a4c021ac33978525f809e3/services/service-catalog.yml#L589-638).
+Each service is assigned a Service Level Indicator (SLI) based on latency using the [apdex](https://www.apdex.org/wp-content/uploads/2020/09/ApdexTechnicalSpecificationV11_000.pdf) standard.
+The corresponding Service Level Objectives (SLOs) for these SLIs require low latencies for large amount of requests.
+It's crucial to ensure that the addition of the routing layer in front of these services does not impact the SLIs.
+The routing layer is a proxy for these services, and we lack a comprehensive SLI monitoring system for the entire request flow (including components like the Edge network and Load Balancers) we use the SLIs for `web`, `git`, and `api` as a target.
+
+The main SLI we use is the [rails requests](../../../development/application_slis/rails_request.md).
+It has multiple `satisfied` targets (apdex) depending on the [request urgency](../../../development/application_slis/rails_request.md#how-to-adjust-the-urgency):
+
+| Urgency | Duration in ms |
+|------------|----------------|
+| `:high` | 250 _ms_ |
+| `:medium` | 500 _ms_ |
+| `:default` | 1000 _ms_ |
+| `:low` | 5000 _ms_ |
+
+#### Analysis
+
+The way we calculate the headroom we have is by using the following:
+
+```math
+\mathrm{Headroom}\ {ms} = \mathrm{Satisfied}\ {ms} - \mathrm{Duration}\ {ms}
+```
+
+**`web`**:
+
+| Target Duration | Percentile | Headroom |
+|-----------------|------------|-----------|
+| 5000 _ms_ | p99 | 4000 _ms_ |
+| 5000 _ms_ | p95 | 4500 _ms_ |
+| 5000 _ms_ | p90 | 4600 _ms_ |
+| 5000 _ms_ | p50 | 4900 _ms_ |
+| 1000 _ms_ | p99 | 500 _ms_ |
+| 1000 _ms_ | p95 | 740 _ms_ |
+| 1000 _ms_ | p90 | 840 _ms_ |
+| 1000 _ms_ | p50 | 900 _ms_ |
+| 500 _ms_ | p99 | 0 _ms_ |
+| 500 _ms_ | p95 | 60 _ms_ |
+| 500 _ms_ | p90 | 100 _ms_ |
+| 500 _ms_ | p50 | 400 _ms_ |
+| 250 _ms_ | p99 | 140 _ms_ |
+| 250 _ms_ | p95 | 170 _ms_ |
+| 250 _ms_ | p90 | 180 _ms_ |
+| 250 _ms_ | p50 | 200 _ms_ |
+
+_Analysis was done in <https://gitlab.com/gitlab-org/gitlab/-/issues/432934#note_1667993089>_
+
+**`api`**:
+
+| Target Duration | Percentile | Headroom |
+|-----------------|------------|-----------|
+| 5000 _ms_ | p99 | 3500 _ms_ |
+| 5000 _ms_ | p95 | 4300 _ms_ |
+| 5000 _ms_ | p90 | 4600 _ms_ |
+| 5000 _ms_ | p50 | 4900 _ms_ |
+| 1000 _ms_ | p99 | 440 _ms_ |
+| 1000 _ms_ | p95 | 750 _ms_ |
+| 1000 _ms_ | p90 | 830 _ms_ |
+| 1000 _ms_ | p50 | 950 _ms_ |
+| 500 _ms_ | p99 | 450 _ms_ |
+| 500 _ms_ | p95 | 480 _ms_ |
+| 500 _ms_ | p90 | 490 _ms_ |
+| 500 _ms_ | p50 | 490 _ms_ |
+| 250 _ms_ | p99 | 90 _ms_ |
+| 250 _ms_ | p95 | 170 _ms_ |
+| 250 _ms_ | p90 | 210 _ms_ |
+| 250 _ms_ | p50 | 230 _ms_ |
+
+_Analysis was done in <https://gitlab.com/gitlab-org/gitlab/-/issues/432934#note_1669995479>_
+
+**`git`**:
+
+| Target Duration | Percentile | Headroom |
+|-----------------|------------|-----------|
+| 5000 _ms_ | p99 | 3760 _ms_ |
+| 5000 _ms_ | p95 | 4280 _ms_ |
+| 5000 _ms_ | p90 | 4430 _ms_ |
+| 5000 _ms_ | p50 | 4900 _ms_ |
+| 1000 _ms_ | p99 | 500 _ms_ |
+| 1000 _ms_ | p95 | 750 _ms_ |
+| 1000 _ms_ | p90 | 800 _ms_ |
+| 1000 _ms_ | p50 | 900 _ms_ |
+| 500 _ms_ | p99 | 280 _ms_ |
+| 500 _ms_ | p95 | 370 _ms_ |
+| 500 _ms_ | p90 | 400 _ms_ |
+| 500 _ms_ | p50 | 430 _ms_ |
+| 250 _ms_ | p99 | 200 _ms_ |
+| 250 _ms_ | p95 | 230 _ms_ |
+| 250 _ms_ | p90 | 240 _ms_ |
+| 250 _ms_ | p50 | 240 _ms_ |
+
+_Analysis was done in <https://gitlab.com/gitlab-org/gitlab/-/issues/432934#note_1671385680>_
+
## Non-Goals
Not yet defined.