Four arm shaft iron farm

An iron farm with four modules arranged around a central shaft, each holding three villagers and a zombie. Golems spawn on the module platforms, walk off into the shaft, and die on campfires or lava with hoppers feeding the chests below. The build itself is quick, most of the work is moving the villagers. Java only.

• Java only, and the video never says so. Several people built the whole thing on Bedrock first. Bedrock needs a different design entirely, with 18 to 20 villagers rather than clusters of three.
• Name tag the zombies or give them an item to hold. The video leaves this out and they despawn.
• Spawnproof any cave within about 12 blocks under the villagers, or the farm breaks.
• The villagers have to sleep now and then. If they panic without a break the spawning stops, so break their line of sight to the zombie occasionally. A sticky piston on a daylight sensor automates it, which matters on servers where night is short.
• Lava kills faster than campfires and a faster kill raises the rate. Put signs on each exposed hopper and drop the lava on the middle sign so no drops burn.
• If you use lava, use crimson or warped fence gates. Ordinary ones catch fire.