SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd4eddb984b70d25fc291979f53c72f2e2c2909548a67cf5400a818f95261e3e4' 
  AND token = 'NslaGQIKJgXmPESvIXbjoNb+Vl57wRb4816beFv0aMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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