SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b76ee7fa9666d4617c3e03c5407ba4b29eb5ff8da55f914d48c597c943a1f575' 
  AND token = 'LQTQPUSV6ulH6zrvoPpMBJqEvNBEnlJOnDAy0TKyYkg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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