SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51dc0effbedc659e0eb3a6c5789c1212558723f169f934e809052acc0a947aca' 
  AND token = 'UCgxDmQ+reOmWsPLIJEVthbdmlTGao+FoJUms+PclnM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00050

JSON explain

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