SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55a3b26844e7f58a888689e3e6ad172030bbe2ed673d3d61fad4e594e3e84a4d' 
  AND token = 'skZx6rFYo6lefqMAvvGq0GoyoN86+ZQ0m54AY+VKMgs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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