SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fd895e35d1df804009fb35df3250d86f92928bd43d22711c1a1b74ee67830464' 
  AND token = 'hqB7bmqbfUC+qqPkKW5JD56De4AEKW0yZTNrjG4yF+s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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