SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '743ec9f08da4163fac93770cde4c07de385b2a2f3d1a0984411ca0516da5750b' 
  AND token = '38VF+gBYyMh3fR2mTw+JPieXImpPrmGzC7WEHBun5dQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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