SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '797ce31170b29575f3085f6fbd149bd63d42037cf87816f9bcb7369361aed354' 
  AND token = 'rnYRK2d5hEXZacHZLsaLpYQ++GWkO6Bj4J6U/ITgcHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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