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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50543971b41fb9bcaeae1c17041dc5d3abe21c5dc112b178004a0612a8493403' 
  AND token = '6UDdMNEQnAMLYIP907M92w4EWDt6BCHyWSjFQlBEutM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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