SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c863b3f64c294eddc89284f17a7dcde365e33a5364503a53144460d5fcdeb4c6' 
  AND token = 'PJElE56vT1UxjQDImesyhk++pNOsHx/vVXNb4mrkNr8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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