SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55f29969429fcba7ef823070b560b1248ab92c51e953c99f546c928d87dadae9' 
  AND token = 'qIIWHnMNfvyoB2IHXpz9hk472q6s3ayIdcTYG/MDYx8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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