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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc608f489cc3be0c4658c2e510a6304f15c5bdc9a2c91af41ed16c0aef2c4644' 
  AND token = 'c2m6kfiUIBf7cV+XvB+2oTEc3LY83CBqMiFd7TtxFg4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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