SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c61d74ae493e8a039cf00a9051996da46a470df21c388f053671e0aa594f4d60' 
  AND token = '71BSUlSsSmqufhnEl0SN6Ov9oMGRDEBZXu6VHYEEf7k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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