SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '346d4c751d54e2f9f42a20026653d1ef581a59700008f5e04455c8bb103d8288' 
  AND token = 'IXv6OBNWQuZPp1V5EMAz/HoRG2yz9NZ+uc60bFAMZs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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