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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ce6a39fb2e3fff12049795635896db1d69f1cb6463fa3e2fb0758e4dd1ce252' 
  AND token = 'MMKOu1K/r+4ttY/+Tp+rEizFMmFsR3cc1eIIPyUwZs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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