SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f51365204d1db04ee07a76b0c9f8bd91185214cabb6527e290ae44836c7f78fb' 
  AND token = 'ump+9W+2hSqYpnN9xTXjMWMfjQ1iPhmj/JFxK89NNL0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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