SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef11d276a09b030d6a88706a6c03f129e79e3f47059c15f519936124b08a86d' 
  AND token = '6R04HNMWyJmSB/9kqHvlgFjGWIy0vA/seXnXySr7PLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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