SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '44a0810fd05f026cb42c08ed4b22fd8fa219da76399d46412ef75761f5bad624' 
  AND token = 'e9iZ+dT4jGQqPNvB2AXPg9hu+EZlIFHHfZzzC9jrXs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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