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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12a8550d1b9a71ad21cdf7ee22997ebb96a92437d13303506873fb4cfe31d9e' 
  AND token = 'kfj+cYp9J1RxZsaVYEQ69WmKJPyaNjhAWiqcHnM13Aw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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