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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8775f4efc0d9b031891b4cf5256c9489785dcd8b94016bd1e52144a6a945b8e' 
  AND token = 'HfpwbKST2HByIJX8wliFkF5fPSIrvOsSb0UI48Ir384=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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