SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12d7978ffdc1f2b1c9a22955ff65ed355ad2bc051a1d21d3354567ebe1b09dbd' 
  AND token = 'n1YAgVSth0NNSdtqGHeQSEeP8rzbgXUs3anr0DZvYsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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