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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de4b9644176212be6e373aa413ed87b8dbc0187c5cbe9018185ee15b9df3f99d' 
  AND token = '6utAhT0BnE+1JfpBQP4QZNMoIy8vsxwz8XOqLpTA7LI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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