SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '85df1c8519a131957cbace3e867211b80b74ef521678a0d751821170dc3ae390' 
  AND token = 'skSp4/R6TNOR7bXs1fhumTtm9PmmxY3tcfsvxpAKTXk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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