SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '08e328d235a462a18d399d13c78bde586f735e764dd1ccfc4ea67fa6945bfc93' 
  AND token = '50GxQRr2/AuGzmcYJUVOf6uhrYCzNftlV2WwtoAOgJY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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