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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a3bdd9fe6b2bcf9628d13579d2f1604339a18b51e521dcd0a97e5fe9c8f23b0' 
  AND token = '6iX9bTEE3v4aUnn6+JpJX6lI6qn0Nu8AAw+dZgCsUgU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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