SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d1612260382c9787c03393715de371e640e12f6f70901eac9e022eb96903359' 
  AND token = 'zKJNUvG9LPpClURk3LhCeLgp9jFRIY8bd+B9zZCVg04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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