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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6340234967511649756795aa903d4fca8f94548936a704738248568b420c8d2' 
  AND token = '8F/1KDQtLYwPaaSC6XKo8Qwpoo0gqzpcW78VcB5a9TA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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