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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '18aee88338629563be73de7c1b6eb91a211adfc4a0c4c6aae8e68e2aad0e558d' 
  AND token = 'cNpLtvPLIjhOf+mKeoFbiYX0K83ZlqKfyPrDvKWpjQ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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