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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b551fcd49c7b5e1b18c22037091e23c52bb416f9e7d37df48aa5ee8ff26b8bbb' 
  AND token = 'JmEN5HHjn3LX1VkWY+3MsFs2hcDJZhDfd/MZdorp0go=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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