SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e0941828679d4db29bb7e13b7262566bd4d7a9cbc04101f38f7e9b01fa73571' 
  AND token = '8mRrLG8wSNB3SXOhNxuG73ZSL5w56e+JqKupFxg/n58=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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