SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd90bb9e6be810d430195dae81984941a03208c5291a83aa3679921c760b55557' 
  AND token = 'sDlhOWb+Fw8T1pQEpL0TrNIgBwnUdwOWhxmfVie6qes=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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