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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8ecac1839312d02edf76e7f723980a02383b59a4f0eaaf76a9376d51238431c6' 
  AND token = 'nm5xDvzRSijyhmC6p2iOOynUrrSy3U8PQAbktcjjmUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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