SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8318e14ffac44bd495e3e44b123c86d0d03f21842063a066b8bce8be2dff23a' 
  AND token = '52J7ERdWBb4rjE6vsYNt4htH2bfFVsPI8poPrhm8TD0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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