Use Cargo to keep factory sites separate

List what each site imports and exports

Write down the materials each site receives, the products it sends out, and the rate it is expected to sustain. If the list gets long, move unrelated production to another site.

Make the useful intermediate steps at the site instead of shipping every material between factories. For example, a site with local ore should usually perform the high-volume early processing there when that reduces the amount that must leave. The exact choice depends on the recipes and rates, so compare the possible export items before building the Cargo links.

Keep a storage depot at each side of an important link. It makes the direction of travel obvious and gives you a place to see whether the sender, the Cargo connection, or the receiving factory is falling behind.

Choose imports and exports before laying out the floor

Start with the finished products assigned to the site. Work backward through their recipes and decide which inputs should be local. Materials that come from nearby nodes are easy choices. For the rest, compare the number of Cargo links with the cost of making another intermediate locally.

Do not import an item only because another factory happens to make it. If the receiving site can make that item from materials it already has, a small local block may be much simpler than another permanent cross-world connection. On the other hand, a complicated low-volume part may be a good Cargo export from one specialist factory.

Once those choices are made, place Cargo receivers near the beginning of the production path and dispatchers near the finished storage. Avoid running an imported item across the whole floor and then bringing a product back to the same side.

1. List the finished products the site will export.
2. List the source materials available nearby.
3. Choose which remaining inputs will arrive by Cargo.
4. Calculate the sustained rate required on every Cargo link.
5. Build short local rails from those inputs toward the finished products.

Use local rails where they are simpler

Cargo does not need to replace every rail. An extractor beside the factory can feed a short local V3 directly. Several high-volume materials moving between neighboring blocks may also fit better on one local rail after you check the combined rate.

Try to keep local rails moving in one general direction. Avoid loops and long branches that reconnect to themselves. When two flows share a V3, add their simultaneous sustained rates on every shared section and keep the total below the 480 items/min Update 1 limit.

Keep local rails inside the site. Once a rail leaves and starts collecting material from other factories, it is part of a shared network again.

When output drops, check the nearest storage first

When a finished product slows down, begin at its input storage. If an imported depot is empty, check the paired sender. If the sender has stock, the Cargo link is the likely problem. If the sender is empty too, follow that site's local production back toward its sources.

With separate sites, you can check one Cargo connection and one local factory instead of following a rail across the world. Before relying on a new site, empty its input storage and make sure it can keep the expected rate.

Some players have reported worse performance in saves with very large connected rail networks and improvement after separating parts of those networks. That remains player-reported behavior, not a guaranteed engine rule. Build separate sites because they are easier to understand and change. Do not expect a performance improvement unless you see it in your own save.