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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50cf0a4de547b200ca824b5ea02b5f8f7d6d09bbce90743589efdfc76c353b72' 
  AND token = 'QgF7ZtDYuCIhkZnRAZQ3ZGzP0rSkJUhoVM46P0rWfKw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}