SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c4b7636942291233b12d528bdbb39a87f0fa0c5057e9b31f4d19b8becaa3b7' 
  AND token = 'Ye7kjzbQIQlHBFki/sgVstW2YtLZY3pbGUGvTvOsT0I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00085

JSON explain

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