SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be6b837cca25191d7115b217eaeb8494fa484da33223b25796d4aeb8c3f2b27b' 
  AND token = 'm0jrwkmvrHHG0HWAorwERnQl2TAYDidok12zSkazlWo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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