SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a81ceb822c3b65f76e5a8acbc9ffbecc9235a5bb35398055ffde0ae7bd9237e1' 
  AND token = 'z6o8cQTDZXwl5ozGXlugBLIx1SY+s47SFpgKvN3HIwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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