SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '791f3c3afe718fd7e12281b529599d945ad784a68aac50e78b45bba3e7e12582' 
  AND token = '6+jsIihjoA/EiNBbDbL/xKSSOxkVZLalRjq9RxSRPIQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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