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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751b0654283ca12c1d488cc68b0a09a2961012e590cb794a6b0595e0dc114d9e' 
  AND token = 'U+8aUBwB0mO050Vmh8BcM0uLuVLqHjJHlXoTqfrsqao=' 
  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"
    }
  }
}