SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '36176342d74a828907e0159833bd4c6ff1ec0a031dc6736b1b47d5c989add842' 
  AND token = '+DVYDuGoJxG8H6injNFFe7BtFPxr4rwZrCOQ7s2+Vmk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}