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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c873194e4f7bceea6104b56f4189718e27235fe1a20e74a52f5b66421358c483' 
  AND token = 'gWr+mjLUGCBNn868uDQy/kIcWgSkuQb0rByI2knJVag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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