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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df5755b61a29e1d0b12cb5919fa9f442c03a13385d2a0a2960ca7b3dbc4ff5ac' 
  AND token = 'X125+x5w4pf/SZ5w4LeJr2VQQ5JrjLb+iRAqGFx/orI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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