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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21da0dc0d0d3f49b741980be8d7a5434b2f1573e9aefa9a7a29fa850646067a' 
  AND token = 'n9+WecfvzfxXOVGz5j/qg/zoKTL09z1Jicp3xdiacNo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}