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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e4eb48a1b50373ed9ebc38e821835dd8f303ce337f996189d20c5f57a58ad587' 
  AND token = 't1/R6PEeOdX5hzGNZreMwTEhclp3ec5nuDzZYkMYkzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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