SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b15e4f38fbdc34892749e7b2c69cc74542ca31ee3fb246db0b431ea5b13993' 
  AND token = 'Xf/Dpg18ahvNcZbuegMNthEFG7XlxJmEBdhUg0GgkqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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