SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2321e91d41091b8c0d9fc7c9cb6df83656e95e33bdf87aa198d03593affdaa75' 
  AND token = 'IcSlSdnEE0REmeS1KR9Ux1SfTTdA+NVAr1BVS2vdjUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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