SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a41a2e5bfea2fe5fe815385e285731c0c7c6db5a122a514e50078de5205de90f' 
  AND token = 'UNlt+V/7BP6VWkBlnVIYWzlU8eg7csLlD4G/d2QhM/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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