SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2019c035786f9a26e9810373fd80fa274b4eee777ef225d0fc30346c6f18a44' 
  AND token = 'ztgiG+s6vkWro82x8wbYDwOVbBMewACG9AuMXD3czOo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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