SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a377d453d03d778afed623911eefa0f28e60920ec51c6c4e306dda4988e49f92' 
  AND token = '2CG0akXE0zMnKskLGRyOMtHHdOBRi8mlscUjNmdiUHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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