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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6d8254591a4e0ddd3cc78280c8d407d84674a482f2dfcbe5cdce44e0a2aba78' 
  AND token = 'XRfoLnXNMctSbVqGp7f1f61ur0NGwuJJnz7LzBQTt+I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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