SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a0a276d145d548f4fcba7fdc133824295c4cf78100e27a24deffdaba577ef0f' 
  AND token = 'FMetEk1lt+RMJtBwABSXwbsSPiLo1/pBrPD+v7c6HQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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