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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31ae10e7ee82afed5b96e3c4e63f576c96dcd4a6cf10b7db84790852294d7d40' 
  AND token = '8LLbiD4+xKKKlsOJo7nk4PJ0t0FkhmSzx3DGwGFkFCU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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