The aim of this customisation is to not run Redis::expire when the ttl is 0, to set no expiration for those keys

CustomSugarCacheRedis.php

<?php

// Enrico Simonetti
// enricosimonetti.com
//
// 2018-08-07 tested on Sugar 8.0.0 on PHP 7.1
// file: custom/include/SugarCache/CustomSugarCacheRedis.php
// The aim of this customisation is to not run Redis::expire when the ttl is 0, to set no expiration for those keys

class CustomSugarCacheRedis extends SugarCacheRedis
{
    // decreased priority from 920 to 919 vs SugarCacheRedis, so that the custom file is used
    protected $_priority = 919;

    /**
     * @see SugarCacheAbstract::_setExternal()
     */
    protected function _setExternal(
        $key,
        $value
        )
    {
        $value = serialize($value);
        $key = $this->_fixKeyName($key);

        $this->_getRedisObject()->set($key,$value);
        if ($this->_expireTimeout !== 0) {
            $this->_getRedisObject()->expire($key, $this->_expireTimeout);
        }
    }
}