SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '760cb71c796257c55b8772398997774c4958e932f3d36576e148481b26b471f7' 
  AND token = '93g1PnRq0semFfhsDt776SgR4EG0mAMoFDUrmGhRmOc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}