Troubles with wordops

Hi there, I have a wordops server based on ubuntu 20.04.4 with php74 on a optmized CPU server with 32GB and 16 cores. I have installed 25 sites and I have around 100k page views daily.

I´m getting problems when a specific site uploads content which gets a lot of concurrent traffic, server is down or can´t connect to database. I launched mysqltuner and there is a few things that I can´t get it solved yet, this is mysqltuner recommendations.

Variables to adjust:
  *** MySQL's maximum memory usage is dangerously high ***
  *** Add RAM before increasing MySQL buffer variables ***
    join_buffer_size (> 256.0K, or always use indexes with JOINs)

Anyone could help on how to get that recommendations ready? This is the full mysqltuner analysis:

[--] Skipped version check for MySQLTuner script
[OK] Logged in using credentials passed on the command line
[OK] Currently running supported MySQL version 10.5.17-MariaDB-1:10.5.17+maria~ubu2004-log
[OK] Operating on 64-bit architecture
 
-------- Log file Recommendations ------------------------------------------------------------------
[!!] Log file  doesn't exist
 
-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE 
^[[D[--] Data in InnoDB tables: 1.2G (Tables: 2881)
[OK] Total fragmented tables: 0
 
-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.
 
-------- Views Metrics -----------------------------------------------------------------------------
 
-------- Triggers Metrics --------------------------------------------------------------------------
 
-------- Routines Metrics --------------------------------------------------------------------------
 
-------- Security Recommendations ------------------------------------------------------------------
[OK] There are no anonymous accounts for any database users
[OK] All database users have passwords assigned
[--] There are 618 basic passwords in the list.
 
-------- CVE Security Recommendations --------------------------------------------------------------
[OK] NO SECURITY CVE FOUND FOR YOUR VERSION
 
-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 5m 40s (819K q [2K qps], 4K conn, TX: 3G, RX: 105M)
[--] Reads / Writes: 99% / 1%
[--] Binary logging is disabled
[--] Physical Memory     : 31.4G
[--] Max MySQL memory    : 381.4G
[--] Other process memory: 0B
[--] Total buffers: 12.6G global + 75.5M per thread (5000 max threads)
[--] P_S Max memory usage: 72B
[--] Galera GCache Max memory usage: 0B
[OK] Maximum reached memory usage: 16.1G (51.24% of installed RAM)
[!!] Maximum possible memory usage: 381.4G (1216.37% of installed RAM)
[!!] Overall possible memory usage with other process exceeded memory
[OK] Slow queries: 0% (0/819K)
[OK] Highest usage of available connections: 0% (47/5000)
[OK] Aborted connections: 0.40%  (20/4948)
[OK] Query cache is disabled by default due to mutex contention on multiprocessor machines.
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 85K sorts)
[!!] Joins performed without indexes: 71
[!!] Temporary tables created on disk: 39% (21K on disk / 55K total)
[OK] Thread cache hit rate: 99% (47 created / 4K connections)
[OK] Table cache hit rate: 78% (857K hits / 1M requests)
[OK] table_definition_cache (10000) is greater than number of tables (3074)
[OK] Open file limit used: 0% (29/500K)
[OK] Table locks acquired immediately: 100% (1K immediate / 1K locks)
 
-------- Performance schema ------------------------------------------------------------------------
[--] Performance_schema is activated.
[--] Memory used by P_S: 72B
[--] Sys schema is not installed.
 
-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.
 
-------- MyISAM Metrics ----------------------------------------------------------------------------
[--] No MyISAM table(s) detected ....
 
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[OK] InnoDB buffer pool / data size: 9.5G / 1.2G
[OK] Ratio InnoDB log file size / InnoDB Buffer pool size: 2.0G * 1/9.5G should be equal to 25%
[--] Number of InnoDB Buffer Pool Chunk: 76 for 1 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 99.86% (51394873 hits/ 51468239 total)
[!!] InnoDB Write Log efficiency: 172.59% (3847 hits/ 2229 total)
[OK] InnoDB log waits: 0.00% (0 waits / 6076 writes)
 
-------- Aria Metrics ------------------------------------------------------------------------------
[--] Aria Storage Engine is enabled.
[OK] Aria pagecache size / total Aria indexes: 128.0M/336.0K
[!!] Aria pagecache hit rate: 88.9% (179K cached / 19K reads)
 
-------- TokuDB Metrics ----------------------------------------------------------------------------
[--] TokuDB is disabled.
 
-------- XtraDB Metrics ----------------------------------------------------------------------------
[--] XtraDB is disabled.
 
-------- Galera Metrics ----------------------------------------------------------------------------
[--] Galera is disabled.
 
-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] Binlog format: ROW
[--] XA support enabled: ON
[--] Semi synchronous replication Master: OFF
[--] Semi synchronous replication Slave: OFF
[--] This is a standalone server
 
-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
    MySQL was started within the last 24 hours - recommendations may be inaccurate
    Reduce your overall MySQL memory footprint for system stability
    Dedicate this server to your database for highest performance.
    We will suggest raising the 'join_buffer_size' until JOINs not using indexes are found.
             See https://dev.mysql.com/doc/internals/en/join-buffer-size.html
             (specially the conclusions at the bottom of the page).
    Temporary table size is already large - reduce result set size
    Reduce your SELECT DISTINCT queries without LIMIT clauses
    Consider installing Sys schema from https://github.com/mysql/mysql-sys for MySQL
Variables to adjust:
  *** MySQL's maximum memory usage is dangerously high ***
  *** Add RAM before increasing MySQL buffer variables ***
    join_buffer_size (> 256.0K, or always use indexes with JOINs)