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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f5eb54b3b3f3e1722c8fc06a0fd726b083f80e362b76b7ccfb4da79d39640fd' 
  AND token = '46/pFuNAq/iM/deT+fkahpAbzzZrAMFoXxYvqARzGTc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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