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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21bee1b3a606b78802a723b3ddcd4bcd805669e82d1c56259e0e29e76901547d' 
  AND token = 'sDbgSMJVaE0rvjjDNZ7faXPXUB1PgHLuw6rxIoxUU0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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