SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '175f7eff2f8d27a353965d65d0fcb16707081b0a7a790030b592041404c3e28f' 
  AND token = 'RGGlDGGkEfina5zBLXw81ZnNZaELaDDQZLh0+UQ2St4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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