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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7d496ee8567a00b63c8f00d39cb18e7b0fafc78a5933bd003ba1ba95c48c312' 
  AND token = 'iIafgKAlUDoZLVwIO8ei95uiWZUsU+gfN8Pa3xe3vZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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