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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c28d1e93479b779be4cef4b8add44f2e156bcfda7d3209735a5fcc76abef0c4c' 
  AND token = 'RKVymDlpF+lMM4FUiDTkzmiQ8IRnUVPmAw0KRjpl4fA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}