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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b2cf470ffcca86bb6fe0e6035320d8ddea5a7b84e028313cbcaac2230be51e' 
  AND token = 'cMJEIGAyxOJ9Rqet5FE9KxEAhn4cm6/aB91PPbttqgc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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