chore(postgres): start articles about replication systems

knowledge base/peerdb.md

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+# PeerDB
+
+Fast, simple, and cost effective Postgres replication.
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+   1. [Sources](#sources)
+
+## TL;DR
+
+<!-- Uncomment if used
+<details>
+  <summary>Setup</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Usage</summary>
+
+```sh
+```
+
+</details>
+-->
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+- [Website]
+- [Main repository]
+- [Documentation]
+
+### Sources
+
+- [Public IPs For PeerDB Cloud]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+<!-- Files -->
+<!-- Upstream -->
+[documentation]: https://docs.peerdb.io/
+[main repository]: https://github.com/PeerDB-io/peerdb
+[website]: https://www.peerdb.io/
+[public ips for peerdb cloud]: https://docs.peerdb.io/peerdb-cloud/ip-table
+
+<!-- Others -->

knowledge base/pg_flo.md

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+# `pg_flo`
+
+Move and transform data between PostgreSQL databases using Logical Replication.
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+   1. [Sources](#sources)
+
+## TL;DR
+
+<details>
+  <summary>Setup</summary>
+
+  <details style="padding: 0 0 0 1em">
+    <summary>Check requirements</summary>
+
+```sql
+sourceDb=> SELECT name,setting FROM pg_settings WHERE name IN ('wal_level','rds.logical_replication');
+          name           | setting
+-------------------------+---------
+ rds.logical_replication | on
+ wal_level               | logical
+(2 rows)
+```
+
+  </details>
+
+```sh
+docker pull 'nats' && docker pull 'shayonj/pg_flo'
+```
+
+  <details style="padding: 0 0 1em 1em">
+    <summary>Configuration file</summary>
+
+[Reference][configuration file reference]
+
+```yaml
+# Replicator settings
+host: "localhost"
+port: 5432
+dbname: "myapp"
+user: "replicator"
+password: "secret"
+group: "users"
+tables:
+  - "users"
+
+# Worker settings (postgres sink)
+target-host: "dest-db"
+target-dbname: "myapp"
+target-user: "writer"
+target-password: "secret"
+
+# Common settings
+nats-url: "nats://localhost:4222"
+```
+
+  </details>
+
+</details>
+
+<details>
+  <summary>Usage</summary>
+
+```sh
+# Start NATS server
+docker run -d --name 'pg_flo_nats' --network 'host' -v "$PWD/config/nats-server.conf:/etc/nats/nats-server.conf" \
+  'nats' -c '/etc/nats/nats-server.conf'
+
+# Start replicator (using config file)
+docker run -d --name 'pg_flo_replicator' --network 'host' -v "$PWD/config/pg_flo.yaml:/etc/pg_flo/config.yaml" \
+  'shayonj/pg_flo' replicator --config '/etc/pg_flo/config.yaml'
+
+# Start worker
+docker run -d --name 'pg_flo_worker' --network 'host' -v "$PWD/config/pg_flo.yaml:/etc/pg_flo/config.yaml" \
+  'shayonj/pg_flo' worker postgres --config '/etc/pg_flo/config.yaml'
+```
+
+</details>
+
+<!-- Uncomment if used
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+```
+
+</details>
+-->
+
+## Further readings
+
+- [Website]
+- [Main repository]
+- [Transformation rules]
+
+### Sources
+
+- [How to set the wal_level in AWS RDS Postgresql?]
+- [Configuration file reference]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+<!-- Files -->
+<!-- Upstream -->
+[configuration file reference]: https://github.com/shayonj/pg_flo/blob/main/internal/pg-flo.yaml
+[main repository]: https://github.com/shayonj/pg_flo
+[transformation rules]: https://github.com/shayonj/pg_flo/blob/main/pkg/rules/README.md
+[website]: https://www.pgflo.io/
+
+<!-- Others -->
+[How to set the wal_level in AWS RDS Postgresql?]: https://dba.stackexchange.com/questions/238686/how-to-set-the-wal-level-in-aws-rds-postgresql#243576