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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e42adaedf71e6acb2e1da749671d6d0f2e7de51b77bbbc028e9691c2016e495a' 
  AND token = 'Q4sMtEiZDgzlVIZw+WS7X2E6i+5tMkmX+oAtWTwr6dw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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