Example MySQL my.cnf optimized

my.cnf

[client]
port    = 3306
socket  = /var/run/mysqld/mysqld.sock

# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket  = /var/run/mysqld/mysqld.sock
nice    = 0
syslog

[mysqld]
# Basic Settings
user      = mysql
pid-file  = /var/run/mysqld/mysqld.pid
socket    = /var/run/mysqld/mysqld.sock
port      = 3306
basedir   = /usr
datadir   = /var/lib/mysql
tmpdir    = /tmp

lc-messages-dir         = /usr/share/mysql
skip-external-locking

# Engine
default-storage-engine  = InnoDB

# Listening IP
bind-address            = 0.0.0.0

# Safety
max-connect-errors      = 1000000
max_allowed_packet      = 64M
skip-name-resolve
sysdate-is-now          = 1
innodb                  = FORCE
innodb-strict-mode      = 1

wait_timeout            = 60
interactive_timeout     = 60

# Buffers
sort_buffer_size        = 4M
read_buffer_size        = 2M
join_buffer_size        = 8M
read_rnd_buffer_size    = 16M

thread_concurrency      = 8 # Max CPU * 2

# MyISAM
key-buffer-size         = 32M
myisam-recover          = FORCE,BACKUP
myisam_sort_buffer_size = 64M

# CACHES AND LIMITS #
tmp-table-size          = 128M
max-heap-table-size     = 128M
query-cache-type        = 0
query-cache-size        = 0
query_cache_limit       = 1M
max-connections         = 5000
thread-cache-size       = 50
thread_stack            = 192K
open-files-limit        = 65535
table-definition-cache  = 1024
table-open-cache        = 2048

# Bin logs
binlog-format           = ROW
log-bin                 = /var/lib/mysql/mysql-bin
log-slave-updates       = 1
expire-logs-days        = 5
sync-binlog             = 1
max_binlog_size         = 100M

server-id = 1 # randomize it incase of multiple servers

# InnoDB
innodb-buffer-pool-size         = 2048M
innodb_buffer_pool_instances    = 8
innodb_additional_mem_pool_size = 20M
innodb_log_buffer_size          = 8M
innodb-log-files-in-group       = 2
innodb-log-file-size            = 256M
innodb-file-per-table           = 1
innodb-flush-log-at-trx-commit  = 1
innodb-flush-method             = O_DIRECT

# With virtual synchrony redundancy, make write queries faster
innodb_doublewrite              = 1

# This is a recommended tuning variable for performance
innodb_locks_unsafe_for_binlog  = 1

# LOGGING
general_log_file                = /var/log/mysql/mysql.log
log-error                       = /var/log/mysql/mysql-error.log
log-queries-not-using-indexes   = 1

[mysqldump]
quick
quote-names
max_allowed_packet  = 16M

[isamchk]
key_buffer    = 16M

#
# * IMPORTANT: Additional settings that can override those from this file!
#   The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/

why bind-address 0.0.0.0 ? not 127.0.0.1 ?

Sure, depends on the use-case.

why bind-address 0.0.0.0 ? not 127.0.0.1 ?

127.0.0.1 == Access Allowed from the self server (Safer)
0.0.0.0 == Access from anywhere in the world / Often used with the port 3306, which allows you to connect with host: example.com:3306 (Not safe)

As replied above, this is just an example.

what's your server hardware configuration? think that is important to know

What are your server hardware configurations?

People - This is old and merely an example, you should use mysql tuner or something else.