SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2521f0ce1f3a6ee938a545ad587739db004f4778285abe35f57e71d90212d392' 
  AND token = 'OinUI56mSvYN+JOSkvuZguLlqocpWiZqTXQ9xVLjzy8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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