SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e17376bff3bbc3077a4197f553a29b45950138a72357c8e45d646f662f67d5d' 
  AND token = '53FS6cY/bOCjGiiNHIawOcwMZmYu8gLtNoprXnDgHnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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