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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6240be2aaad7f2f2f9bc4b34039866c5d04e9ed24a8c82afc53860a78068bd1' 
  AND token = '3CstMsRtc5XuqULLurKxlvLMGNj11HfsYYyEqyif7ws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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