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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c78e9c4e474c4ccd58fbf1dee7b5fa92123c1bd0a7b9ac9ce29a1b648a1c093' 
  AND token = 'MVZpWEcwHu57ujhk0JjjeaRor9zr/DbQNF4yeuVJVAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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