SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375c67e58ba573eb421e204ee487d4046fee35737dc04817e00442ea8f981611' 
  AND token = 'u6CM/5VjBh5ojwXjPCD6S+ncqVz7UinDKTuyd+zi3sE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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