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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '21ca3a938b2228d2ea6754cc42d3c198acbc8bd2d6cdb33848c5ad5069144ccc' 
  AND token = 'NQdDA00pz5LYmsLBUWfa9vJY/hEBBzAYKxZgaR2UcsA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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