SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '940d3b7fc47c513171da2902e2647bebec96fb2f912b6847c58ee48be88ff34b' 
  AND token = 'MTKTgB2vY9+uVbMoph17XnkallXNLV5warqrLKKnAQo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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