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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e97a54435ebef22e32387323c414d75c91f7868de8eae19fbd4b2eb7fd8f345' 
  AND token = 'GVmflJ2FDyzOeveF+jZIbXIXPL9bhuPxvTnZB1g43d0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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