SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b746b0e0e894e42b9611333010c6b86a07ecf2732bce8da72ab66990fe4d3aca' 
  AND token = 'i4duUsXMlmJZFy/fMDUPDWG0Cxp4nysCFBMVbeROh9Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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