SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f8edbfecb8570504cdc976d07cdeca340d9d094f44522da68d88aff429387b7' 
  AND token = '6GQCAejQRGfWeAQmJ8PBRdzUIQqkTlfOCjRdKle0oRU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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