SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d8e3afac41f0785e2d9cc6906274370bc6a375e155ff262cf4f56b0d81084eb' 
  AND token = 'hXQJrDtMzkQtuBlBFQeth53mWRhahXn/VTM2VmML6V8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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