The optimization process and recommendations:

1. Avoid Subqueries (query line: 9): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, it's recommended to join a newly created temporary table that holds the data, which also includes the relevant search index.
2. Avoid Subqueries (query line: 16): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, it's recommended to join a newly created temporary table that holds the data, which also includes the relevant search index.
3. Avoid Subqueries (query line: 25): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, it's recommended to join a newly created temporary table that holds the data, which also includes the relevant search index.
4. Avoid Subqueries (query line: 32): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, it's recommended to join a newly created temporary table that holds the data, which also includes the relevant search index.
5. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.

Optimal indexes for this query:

CREATE INDEX service_idx_applicationid ON Service (applicationId);
CREATE INDEX servicesublayer_idx_sid ON ServiceSublayer (sId);

The optimized query:

SELECT
        DictSchemeName.schemeName,
        DictTableName.tableName 
    FROM
        DictSchemeName,
        DictTableName 
    WHERE
        DictSchemeName.Id = (
            SELECT
                ServiceSublayer.schemeName 
            FROM
                ServiceSublayer 
            WHERE
                ServiceSublayer.sId = 3 
                AND ServiceSublayer.ServiceId = (
                    SELECT
                        Service.Id 
                    FROM
                        Service 
                    WHERE
                        Service.applicationId = 'prga'
                )
            ) 
            AND DictTableName.Id = (
                SELECT
                    ServiceSublayer.tableName 
                FROM
                    ServiceSublayer 
                WHERE
                    ServiceSublayer.sId = 3 
                    AND ServiceSublayer.ServiceId = (
                        SELECT
                            Service.Id 
                        FROM
                            Service 
                        WHERE
                            Service.applicationId = 'prga'
                    )
                )