Nginx https reverse proxy is too slow - nginx

Question

I have Implemented the Nginx cache with https reverse proxy in centos, My response time taking more than 1.5 seconds for each request. My nginx server configuration was 4 core, 8gb ram.
My configuration looks like below (nginx.config)
`user nginx;
worker_processes auto;
worker_rlimit_nofile 100000;
error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;
# Load dynamic modules. See /usr/share/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;
events {
worker_connections 80000;
use epoll;
multi_accept on;
}
http {
ssl_session_cache shared:SSL:10m;
ssl_session_timeout 10m;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
log_format rt_cache '$remote_addr - $upstream_cache_status [$time_local] '
'"$request" $status $body_bytes_sent '
'"$http_referer" "$http_user_agent"';
# Below pattern will print
# Time stamp | Client IP | client Dev apps Name| Request | Status Returned| Time taken in ms| size Returned in bytes| Referer | hit or miss | User agent
log_format bf_log_format '[$time_local]|'
'$remote_addr|'
'$http_x_developer_username|$http_x_forwarded_for|'
'"$request"|'
'$status|$upstream_response_time|$body_bytes_sent|'
'"$http_referer"|'
'"$upstream_cache_status"|'
'"$http_user_agent"';
log_format json_log_format escape=json '{'
'"time": "$time_iso8601",'
'"trace_id": "$request_id",'
'"http": {'
'"body_bytes_sent": "$body_bytes_sent",'
'"x_developer_username": "$http_x_developer_username",'
'"remote_addr": "$remote_addr",'
'"method": "$request_method",'
'"request": "$request_uri",'
'"schema": "$scheme",'
'"request_time": "$request_time",'
'"host": "$host",'
'"uri": "$uri",'
'"user_agent": "$http_user_agent",'
'"status": "$status"'
'},'
'"proxy": {'
'"host": "$proxy_host"'
'},'
'"upstream": {'
'"response_time": "$upstream_response_time sec",'
'"cache_status": "$upstream_cache_status"'
'}'
'}';
# access_log /var/log/nginx/access.log main;
# access_log /var/log/nginx/access.log json_log_format;
access_log off;
sendfile on;
sendfile_max_chunk 512k;
# directio 4m;
# directio_alignment 512;
tcp_nopush on;
tcp_nodelay on;
reset_timedout_connection on;
keepalive_requests 100000;
types_hash_max_size 2048;
# reduce the data that needs to be sent over network -- for testing environment
gzip on;
# gzip_static on;
gzip_min_length 10240;
gzip_comp_level 1;
gzip_vary on;
gzip_disable msie6;
gzip_proxied expired no-cache no-store private auth;
gzip_types
text/css
text/javascript
text/xml
text/plain
text/x-component
application/javascript
application/x-javascript
application/json
application/xml
application/rss+xml
application/atom+xml
font/truetype
font/opentype
application/vnd.ms-fontobject
image/svg+xml;
include /etc/nginx/mime.types;
default_type application/octet-stream;
# Load modular configuration files from the /etc/nginx/conf.d directory.
# See http://nginx.org/en/docs/ngx_core_module.html#include
# for more information.
proxy_cache_path /opt/nginx/cache levels=1:2 keys_zone=api-cache:3000m max_size=100g inactive=43200m use_temp_path=off;
proxy_temp_path /opt/nginx/cache/other;
include /etc/nginx/conf.d/ssl.conf;
}`
My ssl.confg looks like below
server {
server_name _;
root /usr/share/nginx/html;
listen 443 ssl http2 default_server;
listen [::]:443 ssl;
ssl_certificate "/etc/private/ssl/cert.pem";
ssl_certificate_key "/etc/private/ssl/key.pem";
# ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers HIGH:!aNULL:!MD5;
ssl_prefer_server_ciphers on;
keepalive_timeout 100;
# Load configuration files for the default server block.
include /etc/nginx/default.d/*.conf;
location / {
}
error_page 404 /404.html;
location = /40x.html {
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
}
location /health {
default_type application/json;
return 200 '{"status":"UP"}';
}
location /nginx-status {
stub_status;
}
location /trellotest {
proxy_cache_bypass $http_no_cache_purge $arg_nocache;
proxy_cache_methods GET POST;
add_header Cache-Control "public";
proxy_cache api-cache;
proxy_cache_valid 200 40320m;
add_header X-Cache $upstream_cache_status;
add_header X-Time $request_time;
proxy_ignore_headers X-Accel-Expires Expires Cache-Control;
proxy_pass https://mytrelloapp;
}
}
If possible, Anyone could you please advise me if we have anyway to improve the above configurations?