SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b8bd4d7a8f21652c018350390ad29c9cba66214fe2caa8696dcee3bbb4ca233' 
  AND token = 'oUtBunySBt4dZ6P7pxM6AmbasIRNpy7tULuYYcgJJl0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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