SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a9a47279dbf3f1f86f66ef299dd747cbc3fe0b4695ff09b3a18bf829ba275a78' 
  AND token = 'mBdiIJbprwoZvEA9z5U0AD9Ed7sxPRIJhKIXtmmKcGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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