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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f2257ba5f398cd3c5405b3a2c5c1fb90ff8b34d215323b5cc2d8ac35c56a9a' 
  AND token = 'vmB2wbZNAvuLtcCAizL/Ff/kj5GTtH5T1HnvhH0cByM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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