SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a2c6c32850315235388452ff7439e325f6ccc3f720c90631a76560d359939c26' 
  AND token = 'mBwBJG4Qm9338eHBkyqxMRTwW3S8O0r736hSIisx9UI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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