Get count of top level keys from JSON?

[Pramodkuber]

my Splunk logs looks like below. Total keys could change based on use case. I need to get exact number of keys from below data and then what is the max key count among those. Please guide me here.

{
   level: INFO
   logger_name: com.123.logging
   process: NA
   requestId: 1234567
   attribute: email
   criteria: value
   path: aa.bb.cc
   service_name: SERVICE_NAME
   thread_name: h1234567
   timestamp: 2020-09-26T07:33:53.451Z
}

[Richfez]

Do you mean "keys" as in, your example, 'level', 'logger_name', 'process', and so on?

If so, some variant of a search like

index=fw 
| fieldsummary 
| fields field, count
| search count>0 NOT field IN ("date*", "eventtype", "index", "linecount", "punct", "source", "sourcetype", "splunk_server", "splunk_server_group", "tag*", "timeendpos", "timestartpos")
| stats count

might do it.  You'll have to remove the "stats count" at the end to double-check that all the Splunk built-in fields are removed in that `NOT field IN ....` part of the search.