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SELECT 
  vacation_mode 
FROM 
  cscart_companies 
WHERE 
  company_id = 185 
  AND UNIX_TIMESTAMP() BETWEEN cscart_companies.vacation_start_date 
  AND cscart_companies.vacation_end_date

Query time 0.00066

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "Impossible WHERE noticed after reading const tables"
  }
}