SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ebef8ba4d5c9fd47a81ed75c355c3563d1b6f62079356d1bf16a2dbe832a753' 
  AND token = 'XlmSK3p2ZlEBSI+kPXdlyaiCJ/UGqUVrrnqAuP7fkmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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