Conducting assessments with larger and larger cohorts of students is an interesting problem and many possible approaches can be tried, but some are more suitable to some subject disciplines than others.
As already mentioned multiple choice tests are one such technology. They could be computerised quizzes using, perhaps, a VLE (Virtual Learning Environment) or even an online free survey tool. There is also optical scanning of answer sheets for computerised marking of paper quizzes, but my experience shows it has limitations. Writing good multiple choice questions is a skill that needs to be acquired.
There is also peer assessment: getting the students to mark each others papers. Often more effective that you'd expect. This can be done on paper or electronically. When done electronically it can handle anonymisation and also multiple moderation.
You also need to reflect on the goal of assessment. What is it trying to achieve? Are you measuring rote learning memory or understanding and application of knowledge? Sometimes group and team tasks which are assessed by portfolio or presentation can achieve the same goals and deliver less marking burden.
You mention mid-terms. One should also question what function they serve. In many places they are only part of a carrot-and-stick approach to motivate learning and not for the assessment result. In this case they can be substituted with other forms of task which perform the same motivation function in student engagement.