molt-replicator

A guide for continuously copying database changes into CockroachDB after an initial bulk migration. Change data capture, or CDC, reads new changes from a source database and applies them to another database.

In plain words
What is it for?
Use it to configure the post-load replication stage, choose the correct source connector, and manage the handoff from bulk loading to ongoing changes.
Why use it?
It keeps the destination updated while an application is moved from PostgreSQL, MySQL, Oracle, Kafka, cloud storage, or another CockroachDB setup.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/cockroachdb/claude-plugin/molt-replicator
Any agent
npx skills add cockroachdb/claude-plugin --skill molt-replicator
Clone the repo
git clone --depth 1 https://github.com/cockroachdb/claude-plugin

Made for: Claude Code, Codex.

Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,819 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00068 $0.01819
Opus 5 $0.00034 $0.00910
Sonnet 5 $0.00014 $0.00364
Haiku 4.5 $0.00007 $0.00182

Measured 2d ago against content hash 36d6bd17c9fd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

molt-replicator scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl http://localhost:8080/metrics | grep replicator_
Origin

This is a copy

100% identical to molt-replicator — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/cockroachdb-onboarding-and-migrations/molt-replicator/SKILL.md · 205 lines

How it starts

The opening of the file, as written. The whole thing — 205 lines — stays where its author put it; the contents beside it link to each section on GitHub.

molt replicator

Continuous change-data-capture (CDC) replication from source databases to CockroachDB. Run after molt fetch completes the initial bulk load.

Important: replicator is a separate binary from molt. It is not invoked by molt fetch. The data-load-and-replication mode in molt fetch is deprecated — use replicator directly instead.

Architecture

Source DB ──► [replicator] ──► Staging DB (_replicator schema) ──► Target CockroachDB
                  ▲
            Publication/
            Slot/BinLog/
            LogMiner

Replicator reads changes from the source, buffers them in a staging schema on the target CRDB cluster, and applies them to the target tables.

Subcommands by Source

Source Command
PostgreSQL replicator pglogical
MySQL replicator mylogical
Oracle replicator oraclelogminer
Kafka replicator kafka
Cloud storage replicator objstore
CockroachDB CDC replicator start

Full Fetch → Replicator Workflow

Step 1: Initial bulk load with molt fetch

drop-on-target-and-recreate drops any existing target tables first; run this only against a fresh or empty target.

molt fetch \
  --source "postgresql://<user>:<password>@source:5432/db" \
  --target "postgresql://root@crdb:26257/db" \
  --bucket-path "s3://mybucket/migration" \
  --table-handling drop-on-target-and-recreate

Step 2: Create publication on source (PostgreSQL)

-- Run on source PostgreSQL:
CREATE PUBLICATION molt_fetch FOR ALL TABLES;
-- (molt fetch may have already created this; check first)

Step 3: Create staging database on target

-- Run on target CockroachDB:
CREATE DATABASE _replicator;

Step 4: Test connectivity

# preflight only takes --stagingConn and --targetConn (always required for the
# target; stagingConn required if the target is not CRDB)
replicator preflight \
  --stagingConn "postgresql://root@crdb:26257/_replicator" \
  --targetConn "postgresql://root@crdb:26257/db"

Read the full file on GitHub · 205 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 205 lines · 68 tokens per session scan A 36d6bd17c9fd

Subscribe to this mod's changes

molt-replicator is a skill published in the GitHub repository cockroachdb/claude-plugin (4 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 68 tokens to every session and 1,819 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to molt-replicator, differing in 0 lines, and is treated as a copy.

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