[doc-claw-bot]

What is changed, added, or deleted? (Required)

Clarify the concurrency wording in overview.md.

The overview previously said that each TiDB node supports a maximum of 1,000 concurrencies. However, 1,000 is the default value of token-limit, not the maximum. This PR updates the overview to say that each TiDB node supports 1,000 concurrent sessions by default and that you can configure this limit up to 1,048,576.

Which TiDB version(s) do your changes apply to? (Required)

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By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• Related code change PR links (if applicable):
• This PR is translated from:
• Other reference link(s):
  • https://docs.pingcap.com/tidb/stable/overview
  • https://docs.pingcap.com/tidb/stable/tidb-configuration-file#token-limit
  • https://github.com/pingcap/tidb/blob/master/pkg/config/config.go

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• Documentation
  • Clarified that each TiDB node allows up to 1,000 sessions concurrently executing requests by default, configurable up to 1,048,576 with token-limit. The 512-node computing-layer maximum and PB-level cluster-capacity statement remain unchanged.
  • Updated the get token description to specify that token limiting applies when sessions concurrently executing requests on a TiDB instance reach token-limit, and linked to the relevant configuration details.

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ℹ️ Recent review info

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📝 Walkthrough

The documentation now describes per-node concurrent session capacity and clarifies when token limiting applies on a TiDB instance.

Changes: TiDB concurrency capacity

Layer / File(s)	Summary
Session limits and token limiting overview.md, performance-tuning-methods.md	The use-case description states a default of 1,000 concurrent sessions per TiDB node, adjustable up to 1,048,576 through token-limit. The get token description applies token limiting when sessions concurrently executing requests reach token-limit and links to its configuration section.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to adb7e

The overview and performance guidance consistently describe concurrent request-executing sessions, with the stated default and maximum matching the configuration reference. No merge-blocking issue is identified.

### Architecture Summary

Architecture risk: 🔵 Low · up to adb7e

The change affects 2 systems.

Changed systems: overview.md, performance-tuning-methods.md

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — overview.md (service) was modified; 1 changed file maps to changed impact.
• observed — performance-tuning-methods.md (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in performance-tuning-methods.md: The get token limit condition changes from reaching the connection count on a TiDB instance to reaching the number of sessions concurrently executing requests there; the link now targets the token-limit configuration section.
• observed — Modified behavior in overview.md: The use-case description replaces the per-node maximum of 1,000 concurrencies with a default limit of 1,000 sessions executing requests concurrently, adjustable up to 1,048,576 using token-limit; the 512-node computing-layer maximum and PB-level cluster-capacity statement remain.

Pre-merge checks · 5

Passed checks (5 passed)

Check name	Status	Explanation
Description check		The description explains the documentation change, its rationale, affected versions, reference links, and AI involvement. Required sections are present and sufficiently complete.
Title check		The title clearly and concisely describes the main change: clarifying configurable concurrency in the overview documentation.
Docstring Coverage		No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

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ℹ️ Review info

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[Copilot]

🟡 Changes recommended

The wording still risks presenting token-limit as a session cap rather than a concurrent request-execution limit.

2 open findings

• Clarify token-limit controls concurrent request execution · New
• Explain that requests wait when all tokens are in use · New

What changed in this PR

Clarifies how TiDB’s token-limit controls concurrent request execution.

Changes:

• Documents the default and maximum token limits.
• Clarifies token acquisition during SQL processing.

File	Description
overview.md	Updates concurrency limits in the overview.
performance-tuning-methods.md	Clarifies when requests wait for tokens.

🧠 Review effort: Balanced

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-10-20 09:03:41.963210902 +0000 UTC m=+94634.223297819: ☑️ agreed by GMHDBJD.

[lilin90]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lilin90

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #24510.