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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51e86ddc5105a5ec46342512a2a56ebf2c3aa43e2778ed5c8a231cbd3b757ac' 
  AND token = 'mRaPjIM+Mv2JimJ/BZ/5Zf4Q+4YOFITDpf5TFB9xOuU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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