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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f17a77c02f1a8b1b11ebe5600e0bfcd273dd1f19f146be221f835dca5e2aff1b' 
  AND token = 'km5jQHFTe4xQMKkKCmnjsAtVa2+AxPZ8HviYb/BOYHA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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