SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91d6a0e9d503339386abed28984966be7fe75aa7ceaef7f6c2978b5357053d17' 
  AND token = 'facMZhdsNQR+b0mHiN//I3w8o4ohrrwYaOB6L4UYQlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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