SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b31159df1100733b5751b905654981bdcec7f7c86e9a207607ffea1958f3b50' 
  AND token = 'lXb3HwJAa51y7tGIOTbYecynSdjbyHiv4O8GC+m0NJs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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