SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a16d25934541d97fb1a52da105c05e43df718173f135cfe6df096c8ed999e7c' 
  AND token = '4LCsNShBDbYXFMbtlQUWPJC9avxzDDXnWvHLsCapS4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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