Django persistent database connection

I’m using django with apache and mod_wsgi and PostgreSQL (all on same host), and I need to handle a lot of simple dynamic page requests (hundreds per second). I faced with problem that the bottleneck is that a django don’t have persistent database connection and reconnects on each requests (that takes near 5ms).
While doing a benchmark I got that with persistent connection I can handle near 500 r/s while without I get only 50 r/s.

ValueError at /image/ Tensor Tensor(“activation_5/Softmax:0”, shape=(?, 4), dtype=float32) is not an element of this graph

I am building an image processing classifier and this code is an API to predict the image class of the image the whole code is running except this line (pred = model.predict_classes(test_image)) this API is made in Django framework and am using python 2.7