SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c20506db48d6b8fbb5270790bc083f41f71d5632e8e136c691da7819917267a' 
  AND token = 'zawOHQxdUrAexOZlJCoYCe4gZqyKikzMklInE8nmZBs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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