SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d8978a18b9fcf8e1c7e0a7dedde4112d486c1f624cc84f6640591f0ad628549' 
  AND token = 'USHfsPHDIvtNHdwnE6PNjKyhjLXq2Az9BYwikV3zWjA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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