SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '52d99e6c422407ddfbbe1847b6674c9480b31a895570d4ef1b476f5edea54d58' 
  AND token = '68c90WlKqPOEKUBhX3sa5Em8JbamPhwgCEy4RnDv0wY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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