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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8d68861f1a0613e810dd4aa6d9fd7f7c7d2312534e39ac51356e4fa152c8050' 
  AND token = 't+9sYSjMM5h3S+sZ0KAIhWJZjkKn0QI08yb0DYu/2bQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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