SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f4a4253d85e57bbe03c8db4dd5cf36c4cfbef5b1187551ab90e4b4a77b88802' 
  AND token = '5zmIGC++nPz+JxiDzyF9BVGhovu0ebG/up9ZGhTM6Eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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