Types of ways to achieve Many-to-Many relationship between tables in DB?

Question

I have two tables namely 'City' and 'Travels'. City Table will have list of cities in each row with city_id as the Primary Key and Travels Table will have list of travels in each row with travels_id as the Primary key.

Scenario:

One City has many travels for service and One Travels has many city destinations as their service. (i.e) Many-To-Many Relationship in the Table.

         city table                     travels table
+------------+------------+      +-------------+----------------+
|    city_id |  city_name |      | travels_id  | travels_name   |
+------------+------------+      +-------------+----------------+
| 1          | coimbatore |      | 1001        | KPN travels    |
| 2          | mumbai     |      | 1002        | Garude travels |
+------------+------------+      | 1003        | SRT travels    |
                                 +-------------+----------------+
  city_travels join table
+-------------+----------+
| travels_id  | city_id  |
+-------------+----------+
|  1001       |   1      |
|  1001       |   2      |
|  1002       |   1      |
|  1003       |   1      |
|  1003       |   2      |
|  1003       |   3      |
+-------------+----------+

This is how the Many-to-Many relationships between tables are made. But my doubt question is that if either of city table or travels table row increases the city_travels join table row will increase enormously.

Is there any other way to achieve Many-to-Many relationship between tables. I searched a lot but i couldn't find any other solutions.

Please let me know, if there any other options or trick to achieve this. Moreover please comment if there is any wrong in this question.

Thanks a lot in advance

Answer 1

When you get to 100 million rows, we might need another chat. Meanwhile, this describes the optimal schema for many:many.