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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b35a021769e347989f29e6786513f42fc78e3008f08b4089e04505ab0ed8edb3' 
  AND token = 'hit3AISG6ig3l+MZKiYPm3l6QuGfAJjIqV02ysjTFI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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