To solve the preceding business requirement, we will take the 4th approach. We will use – (i) custom metadata type to store the keywords; use (ii) Flow to compare the keywords with the Chatter post body; and, use Process Builder to launch the Flow. Perform the following steps to solve the preceding business requirement:

1. To create a new custom metadata type, navigate to Setup (Gear Icon) | Setup | PLATFORM TOOLS | Custom Code | Custom Metadata Types and click on the New Custom Metadata Type button. Now fill the form as mentioned in the following screenshot:
2. Once you are done, click on the Save button.
3. Create a Text field Keyword to store the words that you want to track in a Chatter post and make this field a required field. At the end, the Chatter Keyword custom metadata type should look like what is shown in the following screenshot:
4. The next step is to insert a few records into the custom metadata type. To do that, click on the Manage Chatter Keywords button on the custom metadata type detail page, and then click on New to insert some records, as shown in the following screenshot:
5. The next step is to create a Flow to implement the business requirement, i.e. create a case from keyword word used in a Chatter post. To do that, navigate to Setup (Gear Icon) | Setup | PLATFORM TOOLS | Process Automation | Flows. Click on the New Flow button; it will open the Flow canvas for you. Create the variables in the Flow, as shown in the following table:
   

   Name	Variable type	Object type	Input/Output type
   VarT_Feedbody	Text	Not applicable	Input and Output
   VarT_FeedItemId	Text	Not applicable	Input and Output
   SovKeyword	SObject variable	Chatter_Keyword__mdt	Input and Output
   SOCVKeywords	SObject Collection variable	Chatter_Keyword__mdt	Input and Output

   We are passing the value to VarT_FeedItemId through Process Builder.

6. The next task is to get all the Chatter post body. For this, we will use the Record Lookup element. To do this, drag and drop the Record Lookup element onto the canvas; it will open a new window for you, where you have to enter the following details:
   1. Name: Enter the name for the Fast Lookup element. In this case, enter Get the Feedbody as the name.
   2. Unique Name: This will be auto-populated based on the name.
   3. Description: Enter a meaningful description.
   4. Look up: Select the object for which you want to search the records. In this case, select FeedItem. The next task is to define the search criteria; for this select Id equals VarT_FeedItemId
   5. Assign the record’s fields to variables to reference them in your flow: Optionally, you can save the fields’ values into variables, so you can use them later in the Flow. Save Body into the VarT_Feedbody variable.
7. The next step is to get all the keywords from custom metadata type. For this, we will use the Fast Lookup element. To do this, drag and drop the Fast Lookup element onto the canvas; it will open a new window for you, where you have to enter the following details:
   1. Name: Enter the name for the Fast Lookup element. In this case, enter Get all keywords as the name.
   2. Unique Name: This will be auto-populated based on the name.
   3. Description: Enter a meaningful description.
   4. Look up: Select the object for which you want to search the records. In this case, select Chatter_Keyword__mdt. The next task is to define the search criteria; for this, select Keyword__c as the field, the does not equal operator, and the global constant {!$GlobalConstant.EmptyString} as the value.
   5. Variable: Use the SObject Collection Variable SOCVKeywords. Do not forget to select the Assign null to the variable if no records are found checkbox. Finally, select the fields whose values you want to store in the SObject variable or SObject Collection variable; in this case, select Keyword__c.
8. The next task is to check whether the SObject Collection variable contains any Keywords or not. I might be possible, there is no record inserted to custom metadata type yet. To check this, we will use the Decision element. To do that, drag and drop the Decision element onto the canvas; it will open a new window for you, where you have to enter the following details:
   1. Name: Enter the name Check SObject Collection Variable Size
   2. Unique Name: This will be auto-populated based on the name.
   3. Description: Enter a meaningful description.
   4. Outcome: Enter the name Not Null as EDITABLE OUTCOME, Select the SObject Collection variable SOCVKeywords as Resource, then is null Operator, and the {!$ GlobalConstant.False} global constant as the value.
9. If the SObject Collection variable is not null, that means that it contains some banned words. We will use the Loop element to extract records from the SObject Collection variable (SOCVKeywords) and store it to the SObject variable (SovKeyword). Click on the Palette tab and drag and drop the Loop element onto the Flow canvas. Map it according to the following screenshot:
10. The next task is to check whether VarT_feedbody – i.e. whether the Chatter post – contains any keywords or not.  To check this, we will use the Decision element. To do that, drag and drop the Decision element onto the canvas; it will open a new window for you, where you have to enter the following details:
    1. Name: Enter the name Lookup for Keywords
    2. Unique Name: This will be auto-populated based on the name.
    3. Description: Enter a meaningful description.
    4. Outcome: Enter the name Found as EDITABLE OUTCOME, Select the variable VarT_Feedbody as Resource, then Contains Operator, and {!SovKeyword.Keyword__c} as the value
11. If the VarT_Feedbody variable contains a keyword, then we have to create a new case. Click on the Palette tab and drag and drop the Record Create element onto the canvas; it will open a new window for you, where you have to enter following details:
    1. Name: Enter the name for the Record Create element. In this case, enter Create a new case as the name.
    2. Unique Name: This will be auto-populated based on the name.
    3. Description: Enter a meaningful description.
    4. Create: Select the Case object. The next task is to assign the value or resource to the object fields (data types must match). To assign a value to multiple fields, click on the Add Row link. Map the fields according to the following screenshot: 
12. Use the connector to connect the elements used in the Flow. Finally, your Flow will look like the following screenshot:
13. Save the Flow (Type: – Autolaunched Flow) with name Chatter Post Keywords Tracking and close the canvas. Don’t forget to Activate the Flow.