SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a376e2f55b1441cb662b399b5ce23787036aa2cc3802a4e64dfdd889798240f' 
  AND token = 'uIhrFIl+6O6KtZlwApdAN8pDIBIqbBmGdYAd8IVBQCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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