SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2ac17a6166a50575ed23bd169d6370a4718f085020ce1cdc181ff93a8beab2d' 
  AND token = 'RB5Zp9NzPsdMFM7SwYr8UfuItdKdOt4uqrKNq2ZCUb4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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