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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251cc6a8afbdb06a08c0902ee5931eb4d1fefd42a4ed4121e8d41dcbf7ab52b5' 
  AND token = 'mGauJjmkA27/gYnfs/DnjeZx1vPWAGrDJILj4XgY2+c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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