SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b3500d386af91950f7b2c1a23c2e7170438e1091b3485244e5b743b505760942' 
  AND token = 'iaFI74t1Kqc/ExhQpGJdkXF5mfCgvsxhEIK4NZInk3g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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