I play on a Realms server with my younger brother.  Our home base is a heavily fortified village.  Several weeks ago, we began getting massive lag spikes whenever we approached the village.  We tried several potential solutions.  First, we moved our livestock away from the village.  That didn't help.  Then we eliminated all the Iron Golems.  That didn't help.  We checked the amount of particle effects in the village and replaced all the Torches with Lanterns or Sea Lanterns.  That didn't help.  Finally, on a whim, we removed the village Beacon.

That did the trick.  Within a few minutes, the lag was almost gone.  We tested this further by burying the Beacon, leaving it "unfed," and even blocking the beam of light it emits.  As long as the Beacon block was placed in the village, the lag was horrific.  When it was removed, the lag stopped.

This never used to happen.  We used to never have lag in our base village.  Something with a recent update messed with the Beacon and made it cause incredibly bad lag.