SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7d51f752157f152bf83a6834022bb5cc3546a8ecf97c7a2b994daeca8c738a9e' 
  AND token = '0MCqGuE2agBbg8/smJN0RFKIpYYt08wRdLoy+twNKHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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