Connection timeouts connecting to Azure Database for MySql Flexible Server (with apparently no resource exhaustion)

We have an ASP .Net 8 Web API hosted on Azure App Service (Windows). It connects to an Azure Database for MySql Flexible Server v5.7, using Pomelo.EntityFrameworkCore.MySql 8.0.2. We are not using Private Access/VNet. It is a multi-tenant application, and all databases are InnoDB databases.

When we were on the older Azure Database for MySql SINGLE server, we never had any connection issues. It had 4 vCores and 32 GB RAM. Since we moved to the newer Azure Database for MySql FLEXIBLE server, also with 4 vCores and 32 GB RAM, we occasionally (and by this, I mean perhaps a dozen times a day) get connection timeout errors like these:

MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
  ---> MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
    at MySqlConnector.Core.ServerSession.OpenTcpSocketAsync(ConnectionSettings cs, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 1046
    at MySqlConnector.Core.ServerSession.ConnectAsync(ConnectionSettings cs, MySqlConnection connection, Int64 startingTimestamp, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 425
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 932
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 938
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 951
    at MySqlConnector.MySqlConnection.OpenAsync(Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 419
    at Microsoft.EntityFrameworkCore.ServerVersion.AutoDetect(String connectionString)
    at PropWorx.API.Extensions.ConfigureExtensions.<>c__DisplayClass5_0.<DbContextConfiguration>b__0(DbContextOptionsBuilder options) in C:UsersfabsrsourcereposPropWorx.APIPropWorx.APIExtensionsConfigureExtensions.cs:line 150
    at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CreateDbContextOptions[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
    at lambda_method134(Closure, Object, HttpContext, IServiceProvider)
    at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
    at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
    at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
    at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
    at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

When this happens, it happens for around a minute, and it affects all users trying to connect at that point. Moreover, although I do see an increase in queries being executed at that point in time (perhaps double the usual) – which most likely is related to the connection timeout – both CPU and RAM usage are low (around 15%) and the connection count is way below the limit of around 4096 (it’s at around 500).

The connection string I’m using in the Web API is pretty basic:

$"Server={serverAddress};UserID={username};Password={password};Database={databaseName};SslMode=Required;TreatTinyAsBoolean=true;ConvertZeroDateTime=true;"

I am using EnableRetryOnFailure:

DbContextOptions<TenantContext> options = new DbContextOptionsBuilder<TenantContext>()
    .UseMySql(connectionString,
        new MySqlServerVersion(ServerVersion.AutoDetect(connectionString)),
        builder => builder.EnableRetryOnFailure())
    .Options;

These are the server parameters we currently have:

aad_auth_only   OFF
aad_auth_validate_oids_in_tenant    ON
audit_log_enabled   OFF
audit_log_events    CONNECTION
audit_log_exclude_users azure_superuser
audit_log_include_users 
audit_slow_log_enabled  ON
auto_generate_certs OFF
auto_increment_increment    1
auto_increment_offset   1
autocommit  ON
automatic_sp_privileges ON
avoid_temporal_upgrade  OFF
azure_innodb_hpk_auto_add   OFF
azure_innodb_hpk_show   OFF
back_log    2831
basedir /mysql/
big_tables  OFF
bind_address    *
binlog_cache_size   131072
binlog_checksum CRC32
binlog_direct_non_transactional_updates OFF
binlog_error_action ABORT_SERVER
binlog_expire_logs_seconds  0
binlog_format   ROW
binlog_group_commit_sync_delay  0
binlog_group_commit_sync_no_delay_count 0
binlog_gtid_simple_recovery ON
binlog_max_flush_queue_time 0
binlog_order_commits    ON
binlog_row_image    MINIMAL
binlog_rows_query_log_events    OFF
binlog_stmt_cache_size  32768
binlog_transaction_dependency_history_size  32000
binlog_transaction_dependency_tracking  WRITESET
block_encryption_mode   aes-128-ecb
bulk_insert_buffer_size 8388608
character_set_client    utf8mb4
character_set_connection    utf8mb4
character_set_database  utf8mb4
character_set_filesystem    binary
character_set_results   utf8mb4
character_set_server    latin1
character_set_system    utf8
character_sets_dir  /mysql/share/charsets/
check_proxy_users   OFF
collation_connection    utf8mb4_general_ci
collation_database  utf8mb4_general_ci
collation_server    latin1_swedish_ci
completion_type NO_CHAIN
concurrent_insert   AUTO
connect_timeout 10
core_file   ON
datadir /app/work/data/
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_authentication_plugin   mysql_native_password
default_password_lifetime   0
default_storage_engine  InnoDB
default_tmp_storage_engine  InnoDB
default_week_format 0
delay_key_write OFF
delayed_insert_limit    100
delayed_insert_timeout  300
delayed_queue_size  1000
disabled_storage_engines    MyISAM,MRG_MyISAM,BLACKHOLE,FEDEATED,ARCHIVE
disconnect_on_expired_password  ON
div_precision_increment 4
end_markers_in_json OFF
enforce_gtid_consistency    ON
eq_range_index_dive_limit   200
error_count 0
error_log_enabled   OFF
error_server_log_file   OFF
event_scheduler OFF
expire_logs_days    0
explicit_defaults_for_timestamp ON
expr_analyzer_cache_type    ON
external_user   
flush   OFF
flush_time  0
foreign_key_checks  ON
ft_boolean_syntax   + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit    20
ft_stopword_file    (built-in)
general_log OFF
general_log_file    /app/work/serverlogs/mysql-general-propworx-san-mysql-flexible-server-57-uszr-2024021909.log
group_concat_max_len    1024
gtid_executed_compression_period    1000
gtid_mode   ON
gtid_next   AUTOMATIC
gtid_owned  
gtid_purged 28ac0c76-cf0b-11ee-a869-6045bd41deab:1-425431,
 8790a5c8-c67b-11ee-b686-6045bd41dbe2:1-1822618
have_compress   YES
have_crypt  YES
have_dynamic_loading    YES
have_geometry   YES
have_openssl    YES
have_profiling  YES
have_query_cache    YES
have_rtree_keys YES
have_ssl    YES
have_statement_timeout  YES
have_symlink    YES
host_cache_size 279
hostname    ba3d1002be29
identity    0
ignore_builtin_innodb   OFF
ignore_db_dirs  
init_connect    
init_file   
init_file_string    
init_slave  
innodb_adaptive_flushing    ON
innodb_adaptive_flushing_lwm    10
innodb_adaptive_hash_index  OFF
innodb_adaptive_hash_index_parts    8
innodb_adaptive_max_sleep_delay 150000
innodb_api_bk_commit_interval   5
innodb_api_disable_rowlock  OFF
innodb_api_enable_binlog    OFF
innodb_api_enable_mdl   OFF
innodb_api_trx_level    0
innodb_autoextend_increment 64
innodb_autoinc_lock_mode    1
innodb_buffer_pool_chunk_size   134217728
innodb_buffer_pool_dump_at_shutdown ON
innodb_buffer_pool_dump_now OFF
innodb_buffer_pool_dump_pct 100
innodb_buffer_pool_filename ib_buffer_pool
innodb_buffer_pool_instances    8
innodb_buffer_pool_load_abort   OFF
innodb_buffer_pool_load_at_startup  OFF
innodb_buffer_pool_load_now OFF
innodb_buffer_pool_size 25769803776
innodb_change_buffer_max_size   25
innodb_change_buffering all
innodb_checksum_algorithm   crc32
innodb_checksums    ON
innodb_cmp_per_index_enabled    OFF
innodb_commit_concurrency   0
innodb_compression_failure_threshold_pct    5
innodb_compression_level    6
innodb_compression_pad_pct_max  50
innodb_concurrency_tickets  5000
innodb_data_file_path   ibdata1:12M:autoextend
innodb_data_home_dir    
innodb_deadlock_detect  ON
innodb_default_row_format   dynamic
innodb_disable_sort_file_cache  OFF
innodb_doublewrite  OFF
innodb_fast_shutdown    1
innodb_fatal_semaphore_wait_threshold   600
innodb_file_format  Barracuda
innodb_file_format_check    ON
innodb_file_format_max  Barracuda
innodb_file_per_table   ON
innodb_fill_factor  100
innodb_flush_log_at_timeout 1
innodb_flush_log_at_trx_commit  1
innodb_flush_method fsync
innodb_flush_neighbors  0
innodb_flush_sync   ON
innodb_flushing_avg_loops   30
innodb_force_load_corrupted OFF
innodb_force_recovery   0
innodb_ft_aux_table 
innodb_ft_cache_size    8000000
innodb_ft_enable_diag_print OFF
innodb_ft_enable_stopword   ON
innodb_ft_max_token_size    84
innodb_ft_min_token_size    3
innodb_ft_num_word_optimize 2000
innodb_ft_result_cache_limit    2000000000
innodb_ft_server_stopword_table 
innodb_ft_sort_pll_degree   2
innodb_ft_total_cache_size  640000000
innodb_ft_user_stopword_table   
innodb_io_capacity  200
innodb_io_capacity_max  2000
innodb_large_prefix ON
innodb_lock_wait_timeout    50
innodb_locks_unsafe_for_binlog  OFF
innodb_log_buffer_size  16777216
innodb_log_checksums    ON
innodb_log_compressed_pages ON
innodb_log_file_size    268435456
innodb_log_files_in_group   2
innodb_log_group_home_dir   ./
innodb_log_write_ahead_size 8192
innodb_lru_scan_depth   1024
innodb_max_dirty_pages_pct  75.000000
innodb_max_dirty_pages_pct_lwm  0.000000
innodb_max_purge_lag    0
innodb_max_purge_lag_delay  0
innodb_max_undo_log_size    1073741824
innodb_monitor_disable  
innodb_monitor_enable   
innodb_monitor_reset    
innodb_monitor_reset_all    
innodb_old_blocks_pct   37
innodb_old_blocks_time  1000
innodb_online_alter_log_max_size    134217728
innodb_open_files   10000
innodb_optimize_fulltext_only   OFF
innodb_page_cleaners    4
innodb_page_size    16384
innodb_print_all_deadlocks  OFF
innodb_purge_batch_size 300
innodb_purge_rseg_truncate_frequency    128
innodb_purge_threads    1
innodb_random_read_ahead    OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads  4
innodb_read_only    OFF
innodb_replication_delay    0
innodb_rollback_on_timeout  OFF
innodb_rollback_segments    128
innodb_sort_buffer_size 1048576
innodb_spin_wait_delay  6
innodb_stats_auto_recalc    ON
innodb_stats_include_delete_marked  OFF
innodb_stats_method nulls_equal
innodb_stats_on_metadata    OFF
innodb_stats_persistent ON
innodb_stats_persistent_sample_pages    20
innodb_stats_sample_pages   8
innodb_stats_transient_sample_pages 8
innodb_status_output    OFF
innodb_status_output_locks  OFF
innodb_strict_mode  ON
innodb_support_xa   ON
innodb_sync_array_size  1
innodb_sync_spin_loops  30
innodb_table_locks  ON
innodb_temp_data_file_path  ibtmp1:12M:autoextend
innodb_thread_concurrency   0
innodb_thread_sleep_delay   10000
innodb_tmpdir   /mnt/temp
innodb_undo_directory   ./
innodb_undo_log_truncate    OFF
innodb_undo_logs    128
innodb_undo_tablespaces 0
innodb_use_native_aio   ON
innodb_version  5.7.44
innodb_write_io_threads 4
insert_id   0
interactive_timeout 28800
internal_tmp_disk_storage_engine    InnoDB
join_buffer_size    262144
keep_files_on_create    OFF
key_buffer_size 8388608
key_cache_age_threshold 300
key_cache_block_size    1024
key_cache_division_limit    100
keyring_operations  ON
large_files_support ON
large_page_size 0
large_pages OFF
last_insert_id  0
lc_messages en_US
lc_messages_dir /mysql/share/
lc_time_names   en_US
license GPL
local_infile    ON
lock_wait_timeout   31536000
locked_in_memory    OFF
log_bin ON
log_bin_basename    /app/work/binlogs/mysql-bin
log_bin_index   /app/work/data/mysql-bin.index
log_bin_trust_function_creators ON
log_bin_use_v1_row_events   OFF
log_builtin_as_identified_by_password   OFF
log_error   stderr
log_error_verbosity 3
log_output  NONE
log_queries_not_using_indexes   OFF
log_slave_updates   ON
log_slow_admin_statements   OFF
log_slow_slave_statements   OFF
log_statements_unsafe_for_binlog    ON
log_syslog  ON
log_syslog_facility daemon
log_syslog_include_pid  ON
log_syslog_tag  
log_throttle_queries_not_using_indexes  0
log_timestamps  UTC
log_warnings    2
logical_server_name propworx-san-mysql-flexible-server-57-uszr
long_query_time 10.000000
low_priority_updates    OFF
lower_case_file_system  ON
lower_case_table_names  1
master_info_repository  TABLE
master_verify_checksum  OFF
max_allowed_packet  536870912
max_binlog_cache_size   18446744073709547520
max_binlog_size 104857600
max_binlog_stmt_cache_size  18446744073709547520
max_connect_errors  100
max_connections 2731
max_delayed_threads 20
max_digest_length   1024
max_error_count 64
max_execution_time  0
max_heap_table_size 16777216
max_insert_delayed_threads  20
max_join_size   18446744073709551615
max_length_for_sort_data    1024
max_points_in_geometry  65536
max_prepared_stmt_count 16382
max_relay_log_size  104857600
max_seeks_for_key   4294967295
max_sort_length 1024
max_sp_recursion_depth  0
max_tmp_tables  32
max_user_connections    0
max_write_lock_count    18446744073709551615
metadata_locks_cache_size   1024
metadata_locks_hash_instances   8
min_examined_row_limit  0
multi_range_count   256
myisam_data_pointer_size    6
myisam_max_sort_file_size   9223372036853727232
myisam_mmap_size    18446744073709551615
myisam_recover_options  OFF
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
mysql_native_password_proxy_users   OFF
net_buffer_length   16384
net_read_timeout    120
net_retry_count 10
net_write_timeout   240
new OFF
ngram_token_size    2
offline_mode    OFF
old OFF
old_alter_table OFF
old_passwords   0
open_files_limit    22741
optimizer_prune_level   1
optimizer_search_depth  62
optimizer_switch    index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosesc...
optimizer_trace enabled=off,one_line=off
optimizer_trace_features    greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
optimizer_trace_limit   1
optimizer_trace_max_mem_size    16384
optimizer_trace_offset  -1
parser_max_mem_size 18446744073709551615
performance_schema  ON
performance_schema_accounts_size    -1
performance_schema_digests_size 10000
performance_schema_events_stages_history_long_size  10000
performance_schema_events_stages_history_size   10
performance_schema_events_statements_history_long_size  10000
performance_schema_events_statements_history_size   10
performance_schema_events_transactions_history_long_size    10000
performance_schema_events_transactions_history_size 10
performance_schema_events_waits_history_long_size   10000
performance_schema_events_waits_history_size    10
performance_schema_hosts_size   -1
performance_schema_max_cond_classes 80
performance_schema_max_cond_instances   -1
performance_schema_max_digest_length    1024
performance_schema_max_file_classes 80
performance_schema_max_file_handles 32768
performance_schema_max_file_instances   -1
performance_schema_max_index_stat   -1
performance_schema_max_memory_classes   320
performance_schema_max_metadata_locks   -1
performance_schema_max_mutex_classes    200
performance_schema_max_mutex_instances  -1
performance_schema_max_prepared_statements_instances    -1
performance_schema_max_program_instances    -1
performance_schema_max_rwlock_classes   40
performance_schema_max_rwlock_instances -1
performance_schema_max_socket_classes   10
performance_schema_max_socket_instances -1
performance_schema_max_sql_text_length  1024
performance_schema_max_stage_classes    150
performance_schema_max_statement_classes    196
performance_schema_max_statement_stack  10
performance_schema_max_table_handles    -1
performance_schema_max_table_instances  -1
performance_schema_max_table_lock_stat  -1
performance_schema_max_thread_classes   50
performance_schema_max_thread_instances -1
performance_schema_session_connect_attrs_size   512
performance_schema_setup_actors_size    -1
performance_schema_setup_objects_size   -1
performance_schema_show_processlist OFF
performance_schema_users_size   -1
pid_file    /app/work/data/ba3d1002be29.pid
plugin_dir  /mysql/lib/plugin/
port    3306
preload_buffer_size 32768
profiling   OFF
profiling_history_size  15
protocol_version    10
proxy_user  
pseudo_slave_mode   OFF
pseudo_thread_id    1503866
query_alloc_block_size  8192
query_cache_limit   1048576
query_cache_min_res_unit    4096
query_cache_size    0
query_cache_type    OFF
query_cache_wlock_invalidate    OFF
query_prealloc_size 8192
rand_seed1  0
rand_seed2  0
range_alloc_block_size  4096
range_optimizer_max_mem_size    8388608
rbr_exec_mode   STRICT
read_buffer_size    131072
read_only   OFF
read_rnd_buffer_size    262144
relay_log   /mnt/relaylogs/relay_bin
relay_log_basename  /mnt/relaylogs/relay_bin
relay_log_index /mnt/relaylogs/relay_bin.index
relay_log_info_file relay-log.info
relay_log_info_repository   TABLE
relay_log_purge ON
relay_log_recovery  ON
relay_log_space_limit   8589934592
replication_optimize_for_static_plugin_config   OFF
replication_sender_observe_commit_only  OFF
report_host 
report_password 
report_port 3306
report_user 
require_secure_transport    OFF
rpl_stop_slave_timeout  31536000
secure_auth ON
secure_file_priv    
server_id   2070254791
server_id_bits  32
server_uuid 28ac0c76-cf0b-11ee-a869-6045bd41deab
session_track_gtids OFF
session_track_schema    ON
session_track_state_change  OFF
session_track_system_variables  time_zone, autocommit, character_set_client, character_set_results, character_set_connection
session_track_transaction_info  OFF
sha256_password_auto_generate_rsa_keys  OFF
sha256_password_private_key_path    private_key.pem
sha256_password_proxy_users OFF
sha256_password_public_key_path public_key.pem
show_compatibility_56   OFF
show_create_table_verbosity OFF
show_old_temporals  OFF
skip_external_locking   ON
skip_name_resolve   ON
skip_networking OFF
skip_show_database  OFF
slave_allow_batching    OFF
slave_checkpoint_group  512
slave_checkpoint_period 300
slave_compressed_protocol   OFF
slave_exec_mode STRICT
slave_load_tmpdir   /mnt/temp
slave_max_allowed_packet    1073741824
slave_net_timeout   60
slave_parallel_type LOGICAL_CLOCK
slave_parallel_workers  32
slave_pending_jobs_size_max 268435456
slave_preserve_commit_order ON
slave_rows_search_algorithms    TABLE_SCAN,INDEX_SCAN
slave_skip_errors   OFF
slave_sql_verify_checksum   ON
slave_transaction_retries   10
slave_type_conversions  
slow_launch_time    2
slow_query_log  OFF
slow_query_log_file /app/serverlogs/slowlogs/mysql-slow-propworx-san-mysql-flexible-server-57-uszr-2024032809.log
socket  /tmp/mysql/mysql.sock
sort_buffer_size    524288
sql_auto_is_null    OFF
sql_big_selects ON
sql_buffer_result   OFF
sql_log_bin ON
sql_log_off OFF
sql_mode    STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER
sql_notes   ON
sql_quote_show_create   ON
sql_require_primary_key OFF
sql_safe_updates    OFF
sql_select_limit    18446744073709551615
sql_slave_skip_counter  0
sql_warnings    OFF
ssl_ca  /app/work/ca.pem
ssl_capath  
ssl_cert    /app/work/cert.pem
ssl_cipher  ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-CCM:DHE-RSA-AES256-CCM:DHE-RSA-AES128-C...
ssl_crl 
ssl_crlpath 
ssl_key /app/work/key.pem
stored_program_cache    256
super_read_only OFF
sync_binlog 1
sync_frm    ON
sync_master_info    0
sync_relay_log  0
sync_relay_log_info 1
system_time_zone    UTC
table_definition_cache  10000
table_open_cache    10000
table_open_cache_instances  16
thread_cache_size   35
thread_handling one-thread-per-connection
thread_pool_new_conn_high_prio  OFF
thread_stack    262144
time_format %H:%i:%s
time_zone   +00:00
timestamp   1711635902.056424
tls_version TLSv1.2
tmp_table_size  16777216
tmpdir  /mnt/temp
transaction_alloc_block_size    8192
transaction_allow_batching  OFF
transaction_isolation   REPEATABLE-READ
transaction_prealloc_size   4096
transaction_read_only   OFF
transaction_write_set_extraction    XXHASH64
tx_isolation    REPEATABLE-READ
tx_read_only    OFF
unique_checks   ON
updatable_views_with_limit  YES
version 5.7.44-log
version_comment MySQL Community Server (GPL)
version_compile_machine x86_64
version_compile_os  Linux
wait_timeout    28800
warning_count   0

Sorry, I didn’t know how to paste an HTML table in this post.
My question is, what else could be the culprit? What else should I look at?

Nothing has changed in our API code. The only thing that’s changed is the type of MySql Server.