SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '51df47ad957961f6b6680f94cc85f0c78168eac9893c0950fc4f2047c0e54087' 
  AND token = '3t5MCYg8nQ3iipMXx3KbLIcZdGGKoyD/HcYIel/lCm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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