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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5c6e57f2c70b29d8d2d4f9478fd100893903eb688a48783c38e2f0c96e20c00' 
  AND token = '86LQBqFdbq1Qcrd5QFrVP1mHfHPu/eEXnI8Ei0MpSLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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