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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8af0f21cc6152c5773e13b570da4c3db2f5768c93fc72bddf4b918afd3d76b2' 
  AND token = 'MtntWlsAx6AJSuuABySODpUl0c0JwtHjyY84Lv8JFCw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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