SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3df715105be7bc701c913a7560d23f16948e441143ca49dfb60469a4a0e882a9' 
  AND token = 'VVrEAP6LVUK4UggbZv7+1RKm7nfjVzUE28lKzcf7qMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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