SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21fed94eb27a8cb9c4761e35230c17fcf04b58e67cfe1172516cab2720f99ddc' 
  AND token = 'MrnpSVvwXYzSGU/cUBITsRGPkJ5ETp768on7OqzRzN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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