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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54ca6b8c5699cbedffe0f3726f323e36c9f142c723dd54c8442d9fe3c07b053d' 
  AND token = '98EM0/ZtPrHMVtFsXo3HSzMMBE3tSms0Kg0SrL/Wjpo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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