Optimizing Sorting and Order Management in CoreData

Sorting is an important feature in my app. I am using integers to represent the ordering sequence.

Items:        A, B, D, E, H
Order number: 0, 1, 2, 3, 4

When I insert a new item "C", here's the outcome:

Items:        A, B, C, D, E, H
Order number: 0, 1, 2, 3, 4, 5

Here's the write operation required on existing order numbers:

D: 2 -> 3
E: 3 -> 4
H: 4 -> 5

I wish to reduce the number of write operations because CoreData is pretty slow at writing. The problem becomes more significant when my users start to have a few thousand items in CoreData.

Here's my current workaround: leaving gaps between each order number. For instance:

Items:        A,  B,  D,  E,  H
Order number: 0, 10, 20, 30, 40

When I insert a new item "C", here's the outcome:

Items:        A,  B,  C,  D,  E,  H
Order number: 0, 10, 11, 20, 30, 40

No write operations are required on existing order numbers.

Every 1 or 2 weeks, when my users close the app, I run background tasks to re-arrange the gaps between order numbers so that when users insert new items, fewer existing order numbers will be affected.

Items:        A,  B,  C,  D,  E,  H
Order number: 0, 10, 20, 30, 40, 50

Since sorting is pretty common, I was thinking some of you might have a better idea on how to reduce write operations on existing order numbers.

If you have a better idea, do you mind to share it with us? Thanks.