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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd49f9133ab0e28fc5b3c9506a338a417a8de58b97d79a3bd65a0eea8dbe3b394' 
  AND token = 'n4gQ8WSgmVlJn94gxHg8XFIUsx04qZ0PaBZADmI+WCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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