SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e791bcae608674158659a67b8ddc3c5e03596babea92911a6e82cc6a8be8d550' 
  AND token = 'CfU0BnsRd7IYeEkDBqIJDThHjsubFPFuf5KbGtHJkGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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