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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8c0cfcb84436f0d6c85bd50f0a343d6ee111c88a9d1ef9e25556dd70489afbd' 
  AND token = 'DG91TBPtMEmLE4IlOuwMJnFsOV7F35QriAE7KrtbmRw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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