SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b56b121e3f087bceee05a5609512f44bc31684fe5511648a3fbfe09f949f16' 
  AND token = 'O475sBIWW5J4kUcPdJejPuIiGli9ScBQ65poP9eGx2o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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