SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76732eda87d3cff9e7b0cde7a96bf1531aedfd046696edb0047eb0da3442a4b7' 
  AND token = 'oubsV2MctTDpXidwrOJVojTutLpGTCDMl1vqmsakIs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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