SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '403291512b15980783ede4485782e6edf1bc1b3c31bc69ecaeba1ac8877f0799' 
  AND token = '5IbRpxyxbVwTnbuM2rfKd8BOi5ofh3bE+gGT3fMyu1A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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