SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79e7839124d26891ec33deed75a2c5eb21603e4e9ca8eb9f5ade391f2f4f901f' 
  AND token = 'png/mxbtrXhwr6OgDJ+VvpG34dXCezZcX8EdCUESqAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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