SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251faeaf903ad626bed8df9faafc10fc70a0fa7afe10d82b2628790130f7e2f0' 
  AND token = 'fs3HXf9Kt+3eofz6FDDWcgikUDuNWGIIwzHAAmBZei8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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