SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7e498a38b6f27426d5a2bca6afda9cd9adefe386f540c0fe9ac760372a75688' 
  AND token = 'QbJ59FXcOslUMjmIQl8GnqJr1BsJynkRJSd43ujkfwQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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