SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ec541f8038813805f5e52dda7add92d9745829a325322dce9051947ef98c141' 
  AND token = 'vPAxAGYi/rsOtDI+7IsHUSpV9iZOY/Zh4a1MyzUHKQA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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