SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a679b01f756779624692e34650b893a207402cf51f135d9f93f88360983679' 
  AND token = 'Ua0i4i+5RlBWmbI9GOGuOKSf+oRAFgOkHDhRD1lQmrk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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