SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9d08df4a9501d13e6570395aa44539c3bb38988bbc7123b38f66d1d083cf5f9' 
  AND token = 'UmJSIVuz2woctcKB+/1j8uvF5FnTf2+GVfwrYtSfJAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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