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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4ee0256372411e3fc23a52450d5ea6bc6d5b0768af5adde644042dd9b7e9472' 
  AND token = 'Mm3bSzJMbZBlXZo0oc7eoxSE8dTTy5JbqPrbfF+RQdE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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