SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ac143f07b368aff83498ed38e824093307ce75cde521db1d6d29513e4aa7b31' 
  AND token = '/LNeBfoKA9DpsUj3ln0CzV3fUjBUcMX6FxjHjiu5wZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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