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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '668cd78adcee9f3b40e7d754e9f07fd9941a4494208dfcf28e12c8bc0457499f' 
  AND token = '9+kETtyItLXprbInuhBpvaGNtI4cR4+NpjthD+C9avE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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