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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b28208e58e8164d72a97b56049bd81c450c0a23725c418d6aedf025c1a3ab641' 
  AND token = 'PDZChKev1ruPDZj67q+R/8k03emMp2QOOL2s54029S4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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