SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76aa2f8ca5c4d37c1138aec478b8db3cff4a7eda9e563c9957b9cbf744aeb799' 
  AND token = 'isriiSklacDY7BfJvsgTXfPrO9YRaSM6o8rPAq+GOKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}