Selecting the oldest updated set of entries - mysql

Question

I have the following table my_entry:
Id int(11) AI PK
InternalId varchar(30)
UpdatedDate datetime
IsDeleted bit(1)
And I have the following query:
SELECT
`Id`, `InternalId`
FROM
`my_entry`
WHERE
(`IsDeleted` = FALSE)
AND ((`UpdatedDate` IS NULL
OR DATE(`UpdatedDate`) != DATE(STR_TO_DATE('17/10/2019', '%d/%m/%Y'))))
ORDER BY `x`.`UpdatedDate`
Limit 200;
The table has around 3M records, I have a program running that executes the above query and returns 200 entries from the table that weren't updated today, the program then changes those 200 entries and updates them again setting the UpdatedDate to today's date, on the next execution those 200 entries will be ignored, and new 200 entries will get selected, this keeps running until all the entries in the table are selected and updated for today.
This way I can ensure that all the entries are updated at least once every day.
This works perfectly fine, for the very first thousands of entries, the select query executes in a couple of milliseconds, but as soon as more entries are updated and have today's date in the UpdatedDate the query keeps slowing down, reaching execution times up to 20 seconds.
I'm wondering if I can do something to optimize the query, or if there is a better approach to take without using the UpdatedDate.
I was thinking of using the Id and paginating the entries, but I'm afraid this way I might miss some of them.
What I already tried:
Adding indexes to both the UpdatedDate and IsDeleted.
Changing the UpdatedDate type from datetime to date.
Edit:
MySql version: 5.6.45
The table in hand:
CREATE TABLE `my_entry` (
`Id` int(11) NOT NULL AUTO_INCREMENT,
`InternalId` varchar(30) NOT NULL,
`UpdatedDate` date DEFAULT NULL,
`IsDeleted` bit(1) NOT NULL DEFAULT b'0',
PRIMARY KEY (`Id`),
UNIQUE KEY `InternalId` (`InternalId`),
KEY `UpdatedDate` (`UpdatedDate`),
KEY `entry_isdeleted_index` (`IsDeleted`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=8204626 DEFAULT CHARSET=utf8mb4
The output of the EXPLAIN query:
+----+-------------+-------+-------+-------------------------------------+-------------+---------+------+------+---------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+-------------------------------------+-------------+---------+------+------+---------------+
| 1 | SIMPLE | x | index | "UpdatedDate entry_isdeleted_index" | UpdatedDate | 4 | NULL | 400 | "Using where" |
+----+-------------+-------+-------+-------------------------------------+-------------+---------+------+------+---------------+
Example of data in the table:
+------------+--------+---------------------+-----------+
| InternalId | Id | UpdatedDate | IsDeleted |
+------------+--------+---------------------+-----------+
| 328044773 | 552990 | 2019-10-17 10:11:29 | 0 |
| 330082707 | 552989 | 2019-10-17 10:11:29 | 0 |
| 329701688 | 552988 | 2019-10-17 10:11:29 | 0 |
| 329954358 | 552987 | 2019-10-16 10:11:29 | 0 |
| 964227577 | 552986 | 2019-10-16 12:33:29 | 0 |
| 329794593 | 552985 | 2019-10-16 12:33:29 | 0 |
| 400015773 | 552984 | 2019-10-16 12:33:29 | 0 |
| 330674329 | 552983 | 2019-10-16 12:33:29 | 0 |
+------------+--------+---------------------+-----------+
Example expected output of the query:
+------------+--------+
| InternalId | Id |
+------------+--------+
| 329954358 | 552987 |
| 964227577 | 552986 |
| 329794593 | 552985 |
| 400015773 | 552984 |
| 330674329 | 552983 |
+------------+--------+

Answer 1

First, simplify the date arithmetic. Then take the following approach:
Take NULL values in one subquery
Take rows on the date in another
Then order and select the results
Start by writing the query as:
SELECT Id, InternalId
FROM ((SELECT Id, InternalId, 2 as priority
FROM my_entry
WHERE NOT IsDeleted AND UpdatedDate IS NULL
LIMIT 200
) UNION ALL
(SELECT Id, InternalId, 1 as priority
FROM my_entry
WHERE NOT IsDeleted AND UpdatedDate <> '2019-10-17'
LIMIT 200
)
) t
ORDER BY priority
LIMIT 200;
The index that you want is either (updateddate, isdeleted) or (isdeleted, updateddate). You can add id and internalid.
The idea is to select at most 200 rows from the two subqueries without sorting. Then the outer query is sorting at most 400 rows -- and that should not take multiple seconds.