SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '25c19b81a403103befafed6488dac26a7556bc982f5567b300554ade1e6780ac' 
  AND token = 'uGDUNMzF7c5RioedNzfl0jU22bqCiC05Nr3cRDQl3oo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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