SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7b7b94c28f9784d3cd7caafee5a15abe37dbefc0784938d3682139d7b278857' 
  AND token = 'NhKUwlhqvyNecZmmnAvtiJi2ZFFAng8G5bU1T28PQKA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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