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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3746854ddbfd4e72d5f0db0e5b8ec1536b61e8baf804518c1c060d57b878b95' 
  AND token = 'rkuMxD9dsFojbJyaIGtsEc6nY6BgsF4ji14xbrqXkcs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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