5. Synchronous Apex
• Occurring at the same time.
• Quick and Immediate actions.
• Transactions are immediate and serial.
• Normal Governor Limits
Asynchronous Apex
• Not occurring at the same time.
• Executes when resources are available.
• Not immediate.
• Higher Governor Limits.
6. Governor Limits
Description Synchronous Limit Asynchronous Limit
Total number of SOQL queries
issued
100 200
Total number of records
retrieved by SOQL queries
50000 50000
Total number of records
retrieved by
Database.getQueryLocator
10000 10000
Total number of SOSL queries
issued
20 20
Total number of records
retrieved by a single SOSL query
2000 2000
Total number of DML
statements issued
150 150
Total heap size 6 MB 12 MB
Maximum CPU time on the
Salesforce servers
10000 ms 60000 ms
7. Example scenario
Update a record Trigger will fire
Need to insert more
than 10000 or query
50000 records
Use asynchronous
apex
Transaction
completes. But
asynchronous apex
may still be running.
9. Future Apex
• @future annotation at the start of method.
• Always method should be public static and return type should be void.
• The specified parameters must be primitive data types, arrays of primitive data
types, or collections of primitive data types; future methods can’t take objects as
arguments.
• Future methods won’t necessarily execute in the same order they are called. In
addition, it’s possible that two future methods could run concurrently, which
could result in record locking if the two methods were updating the same record.
• You’re limited to 50 future calls per Apex invocation, and there’s an additional
limit on the number of calls in a 24-hour period.
• Cannot call another future method from a future method.
10. Batch Apex
• Has a different syntax.
• Every transaction starts with a new set of governor limits.
• If one batch fails to process successfully, all other successful batch transactions
aren’t rolled back.
• Start, Execute and Finish are the 3 methods.
• Can track the progress of batch in the apex job page in setup.
• 5 batch jobs at a given time
• You can call another batch from batch or queue but not future method.
• What happens when more than 5 batch jobs are invoked?
11. Queueable Apex
• Similar to future apex.
• Accepts non primitive datatypes too.
• Can call another queue. (Only one)
• Progress can be tracked in apex batch jobs page.
• You can add up to 50 jobs to the queue with System.enqueueJob in a single
transaction.
12. Schedulable Apex
• Runs apex class at a specified time and frequency.
• Can be scheduled in UI or using cron jobs.
• Scheduled jobs can be tracked from scheduled jobs page in setup.
• You can only have 100 scheduled Apex jobs at one time
Note: Always asynchronous apex should be executed within startTest() and
stopTest().
