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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd6a7bf3f02c2729e2cbf0b1a6803aaaee34e3655c01f29b3c34ecb580f4db3c' 
  AND token = 'rB92W+az9cKQCCrwq2VGZjwXyuKs5GERT8H5DAQoFkU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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