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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb8f9a060ecfe28ad336216515794eef7ab7100d9ecac26b5b68e9b04a50fe38' 
  AND token = 'k5mnfUO4Ds/PuF7XaJlQuZ7nY0qB7R+rfx/pjRL4Lno=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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