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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1a6c9f3203a4baf07ee25f3b69169a8ff00a5491c25b3f79d1ac71f18cffcb8' 
  AND token = 'sMJkRFkt/PfXUzpPkvlQ7tmHbOHVWhpCe+Qf/FC02Zw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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