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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ec5b4e87e73773b91e5b4cdf6c04949027b0a274aa363b35c3a365841e5aea6' 
  AND token = 'v2v4Y3e/vfQXvpXWgOX+dVfT892Y/Aoz4vFyGTCFzkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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