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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6fc1e8c6e3667b323cb3e5dc116db71730503f94c80fca5ca9458380a02df4c1' 
  AND token = 'v5rzlAdUCZ82CFbZlbAClsYHYlCrIhDkuY4B+t25gRg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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