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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7e814dbf0f42801503a696f89a0fa427cf0da612b57ec6bdd86bedc5d647fc54' 
  AND token = '3kmdaa0U9ffIa/cMjpve3QrlP9VG7QJh6T7H/QPB1Ng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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