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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '506d08a57f8efb714c38c3e0cc9f3b819cabf5f5df6518e696933f614e4d6e7c' 
  AND token = 'xy//pS6hUoZTflv0P1Ze+2+M1y+KLfDpWbXMXiJpVPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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