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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '81fb801681079f76f73d4f182714e327202d143199dd0445ae4211987f40165c' 
  AND token = 'f3MDIMCdfumCkoMBG2B8nGiwyAMIB3qFG6+p2ymtjBc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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