Upgrading MySQL 5.7 to 8.0 on AWS RDS is a necessary move for long-term security and supportability.
MySQL 5.7 is end-of-life upstream, and even with extended support options, staying current reduces operational and security risk.

One major prerequisite before the version jump is updating character sets from utf8mb3 to utf8mb4.

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Upgrade checklist

1. Take a reliable backup/snapshot.
2. Convert table and column character sets to utf8mb4.
3. Handle NO_ZERO_IN_DATE / NO_ZERO_DATE behavior in sql_mode.
4. Run the engine upgrade to MySQL 8.0.
5. Validate application behavior and query compatibility.

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1) Backup first

Before modifying schema or parameter groups:

• Create an RDS snapshot.
• Confirm restore works (or at least validate snapshot availability and retention).
• Plan a rollback window before changing the engine version.

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2) Convert tables from utf8mb3 to utf8mb4

Generate table conversion statements:

SELECT CONCAT(
  'ALTER TABLE ', table_name,
  ' CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;'
)
FROM information_schema.tables
WHERE table_schema = 'YourDBName'
  AND table_collation LIKE 'utf8%'
  AND table_collation <> 'utf8mb4_unicode_ci';

Copy generated output and run it in a separate query tab.
If the session drops or timeouts occur, rerun until all target tables are converted.

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3) Convert columns from utf8mb3 to utf8mb4

Generate column-level conversion statements:

SELECT CONCAT(
  'ALTER TABLE ', table_name,
  ' MODIFY ', column_name, ' ', column_type,
  ' CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;'
)
FROM information_schema.columns
WHERE table_schema = 'YourDBName'
  AND character_set_name LIKE 'utf8%'
  AND collation_name = 'utf8_general_ci';

Run the generated statements and verify results.
This is especially important for text columns that still carry legacy collation.

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4) Handle zero date/datetime/timestamp compatibility

If your data includes zero-date style values, strict SQL modes can break writes/reads after upgrade.

Create or use a custom parameter group

• RDS Console -> Parameter groups
• Engine: MySQL Community Edition
• Family: mysql8.0

Update sql_mode

Edit sql_mode and remove:

• NO_ZERO_IN_DATE
• NO_ZERO_DATE

Save changes and attach this parameter group to the DB instance.

Apply and reboot

• Modify DB instance to use the custom parameter group.
• Apply immediately (or during maintenance window).
• Reboot the instance so parameter changes take effect.

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5) Run the RDS engine upgrade

Start the MySQL version upgrade in RDS after charset/collation cleanup and parameter alignment.
Upgrade duration varies by size and workload; small-to-medium environments often complete within tens of minutes.

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Post-upgrade validation

• Check app connectivity and auth plugins.
• Validate key queries and stored procedures.
• Confirm collation/charset on critical tables.
• Review error logs for SQL mode and deprecated syntax warnings.

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Final notes

The safest path is preparation first: backups, charset normalization, and parameter compatibility.
With those done, the MySQL 8.0 upgrade is much smoother and reduces production surprises.