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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b2f116eae6b5744d67415db8b6d65b9bc8aa3cb1c48df2ae0a59b54df90bd658' 
  AND token = 'MY1VsalFJOLg+D9rVABxuTFfLe59N30dO7CHs38fl04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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