SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d323f53b8eaa1ea18c2db5df0a1eba2172634bd7a35271ed40888ff92b9ce1' 
  AND token = 'LxLbgwbYLEHMMezo2o3ZkhofccoYDzYDR4xvMJ8TBnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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