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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'eb43e4e6f658285cd582c7c5e622fb8fe158c2b0c9ecd555c09072ff3c5fb263' 
  AND token = 'DcI3KU+IMsNxfseRAJ/gRQAcE8N+S0zNECFHRgc2jZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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