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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68848e903303ec444a714499573096c52f57f3122261ac223c5c02fa8976502b' 
  AND token = 'W81n1dabHbWvf29XoFhW8uGthW3JtdtgagaTyjTPgac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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