SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9db2f40ab2487a052e083463416df5ae75b98634c5556803d007dc8889c2044c' 
  AND token = 'QHwCaxMqUAWhUPIbE6Evw7PaHnXV1xlwfmzFDCv/DSU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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