SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df59def17d3efd3dd075a033fa270d7f5b06873ae8d4795ab47fcef902dab8c8' 
  AND token = 'iel7qM39cAb8EBT1YdGbxtiuM/FzRBKYOmfQTHtTUoY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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