High Availability — Complete Guide
High Availability — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of MySQL Tutorial on Toolliyo Academy.
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MySQL Tutorial · Lesson 79 of 100
High Availability
Basics ✓ → Advanced
Advanced · 2 — Production · ~10 min · MySQL — Advanced MySQL
What is this?
High availability (HA) keeps MySQL reachable through failover: InnoDB Cluster, Group Replication, or managed multi-AZ RDS with automatic primary promotion when node dies.
Why should you care?
Single mysqld on one VPS — disk failure takes Swiggy-style ops offline. HA targets minutes not hours downtime.
See it live — copy this example
Run in MySQL Workbench or the mysql CLI.
-- Managed HA check (RDS/Aurora style):
SELECT @@innodb_read_only AS read_only_flag,
@@global.read_only;
-- During failover brief errors; apps retry connectionsWhat happened?
- read_only=1 on replica.
- During failover promoted replica becomes writable primary.
- Apps use DNS/endpoint that tracks current writer; connection pools must retry on transient errors.
Practice next
- Document primary endpoint vs reader endpoint for cloud.
- Test app reconnect after stopping local mysqld (dev).
- Enable multi-AZ on staging RDS if using AWS lesson.
- Simulate DNS swap to new primary in staging.
- Measure RTO/RPO targets for DataFlow SLA doc.
Remember
HA = automatic or fast manual failover. Apps must retry and refresh connections. Multi-AZ / Group Replication common patterns.
DataFlow multi-AZ RDS
AZ outage triggers standby promotion — app errors 30s then recovers.
Outcome: Checkout resumes without manual DBA wake-up.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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