SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75923b99bef8be862e949ce406075fb75521f382fa77cc7192b2b6264c878cac' 
  AND token = 'dvKKCAbpreTQdv+A/1PsoYmSsGmk9FMybfcmVyhB3/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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