[{"firstName":"Hulda","lastName":"Lamb",},{"firstName":"Austin","lastName":"Todd",},{"firstName":"John","lastName":"Doe",}]

db.collection.aggregate([{$sort:{firstName:1}},{$group:{_id:null,docs:{$push:"$$ROOT"}}},{$project:{nextNPeople:{$slice:["$docs",{$add:[{$indexOfArray:["$docs.firstName","Austin"]},1]},1]}}},{$unwind:"$nextNPeople"},{$replaceRoot:{newRoot:"$nextNPeople"}}])