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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b8801b6de6dd178300d66666e9a5e3fded3d3a3ba5e8e9e4d3d14dbdd87bd9' 
  AND token = '2lVeFLYwlPGfIqbaQ5adaxnghFNKXqWxST1yrbXcDKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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