SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9a8b8e974a68ed4091db2c1b231e44816b858a4fb652032f377b25c6aa431e6' 
  AND token = '7PJNVlOYOV2OY863gnMvVv7ejE0iioxi8fRsGi6UMIo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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