Do not keep connections open longer then necessary to reduce resource usage and deny Slowloris type attacks.

client_body_timeout 3s; # maximum time between packets the client can pause when sending nginx any data
client_header_timeout 3s; # maximum time the client has to send the entire header to nginx
send_timeout 3s; # maximum time between packets nginx is allowed to pause when sending the client data
keepalive_timeout 9s; # timeout which a single keep-alive client connection will stay open
keepalive_requests 10;  # number of requests per connection, does not affect SPDY
keepalive_disable none; # allow all browsers to use keepalive connections

Size limits

# Size Limits
client_body_buffer_size 8k;
client_header_buffer_size 1k;
client_max_body_size 10m;
large_client_header_buffers 4 4k;


# Extra security headers
server_tokens off;
add_header X-Frame-Options SAMEORIGIN;
add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";
add_header Strict-Transport-Security "max-age=7776000; includeSubDomains; preload";

TLS configuration

ssl_protocols TLSv1.3;
ssl_prefer_server_ciphers on; 
ssl_ecdh_curve secp384r1; 
ssl_session_timeout 10m;
ssl_session_cache shared:SSL:10m;
ssl_session_tickets off;
ssl_stapling on;
ssl_stapling_verify on;
resolver valid=1800s;
resolver_timeout 5s;