SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '98df84bbaafc3f0af1300cfe76e708b2edcbddc2800298b553644f86af878af5' 
  AND token = 'G5a3F/5RdbVfeX8dRIYiIZKXcqeI1kRUEV+9ijEAVNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}