SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3a0c26ae8d048a7f68658a82b2cf0a4c784c7cb897063ce50dbb68a5c536196' 
  AND token = 'tY9X0taPK/0VvBJOj+oznXfbvmAVSlreRjuzXxckyZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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