SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2373ce4c6febe944f1699e579ad5e606a9d51d3b22b6fd20c76a8b03d550bc96' 
  AND token = 'WL51JWhwf8N2QUYDfX5CO02pldsKbboGwmLefEYh8ZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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