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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21cae0d11d9bff0aff299c2b755f679395da0811dc741fc6cc476a97e3530dcd' 
  AND token = 'ojElw2KYJwcwjqJTfnoThvXNXg2TLUYkkQmLHXylMtM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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