SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d73c3163548eaf1cf4400e7d8697fc901a4e51637688f9a9534e2c2a5758ee3' 
  AND token = '6xwvzngYLBKKCW+MOVXNlfRcEacC0sIjs0VAorZmzdY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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