SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '305c590b3646e312c467bfe4de24705b6c6708d0a32c156cb9653fa629455614' 
  AND token = 't83Za0U9z9d2sgHsDEyqB6OzyTNnl6riN0PcsWbMUVU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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