SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c9b2e7b74c678f5b9a577686400f644dfbde250ea7072c687dd72bfd738e42a' 
  AND token = 'LjYHdeSIWc0RKqQzaCS/WH/wEiE2oMvKRjzGjFk/ZsA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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