SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '851b39841aace6fdd6212e009651c47cd7f27f03e2209f25f53ba4fffdbcfe70' 
  AND token = 'E3H9WaYvFLDxcDh/NGjWURDlK58HV6lDnCQdhB6obqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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